diff --git a/src/main/java/net/spy/memcached/ArcusClient.java b/src/main/java/net/spy/memcached/ArcusClient.java
index 89ee5cea0..4a2b4df17 100644
--- a/src/main/java/net/spy/memcached/ArcusClient.java
+++ b/src/main/java/net/spy/memcached/ArcusClient.java
@@ -655,7 +655,7 @@ public void complete() {
             latch.countDown();
           }
 
-          public void gotData(String subkey, int flags, byte[] data, byte[] eflag) {
+          public void gotData(String elementKey, int flags, byte[] data, byte[] eflag) {
             cachedDataList.add(new CachedData(flags, data, tc.getMaxSize()));
           }
         });
@@ -711,7 +711,7 @@ public void complete() {
             latch.countDown();
           }
 
-          public void gotData(String subkey, int flags, byte[] data, byte[] eflag) {
+          public void gotData(String elementKey, int flags, byte[] data, byte[] eflag) {
             cachedDataSet.add(new CachedData(flags, data, tc.getMaxSize()));
           }
         });
@@ -814,18 +814,18 @@ public void gotData(String mkey, int flags, byte[] data, byte[] eflag) {
    * Public methods for collection items call this method.
    *
    * @param key             collection item's key
-   * @param subkey          element key (list index, b+tree bkey)
+   * @param elementKey      element key (list index, b+tree bkey)
    * @param collectionInsert operation parameters (value, eflags, attributes, and so on)
    * @param tc              transcoder to serialize and unserialize value
    * @return future holding the success/failure of the operation
    */
   private <T> CollectionFuture<Boolean> asyncCollectionInsert(String key,
-                                                              String subkey,
+                                                              String elementKey,
                                                               CollectionInsert<T> collectionInsert,
                                                               Transcoder<T> tc) {
     CachedData co = tc.encode(collectionInsert.getValue());
     collectionInsert.setFlags(co.getFlags());
-    return asyncCollectionInsert(key, subkey, collectionInsert, co);
+    return asyncCollectionInsert(key, elementKey, collectionInsert, co);
   }
 
   /**
@@ -833,30 +833,30 @@ private <T> CollectionFuture<Boolean> asyncCollectionInsert(String key,
    * Public methods for collection items call this method.
    *
    * @param key             collection item's key
-   * @param subkey          element key (list index, b+tree bkey)
+   * @param elementKey      element key (list index, b+tree bkey)
    * @param collectionInsert operation parameters (value, eflags, attributes, and so on)
    * @param co              transcoded value
    * @return future holding the success/failure of the operation
    */
   <T> CollectionFuture<Boolean> asyncCollectionInsert(final String key,
-                                                      final String subkey,
+                                                      final String elementKey,
                                                       final CollectionInsert<T> collectionInsert,
                                                       final CachedData co) {
     final CountDownLatch latch = new CountDownLatch(1);
     final CollectionFuture<Boolean> rv = new CollectionFuture<>(
             latch, operationTimeout);
-    Operation op = opFact.collectionInsert(key, subkey, collectionInsert,
+    Operation op = opFact.collectionInsert(key, elementKey, collectionInsert,
             co.getData(), new OperationCallback() {
               public void receivedStatus(OperationStatus status) {
                 CollectionOperationStatus cstatus = toCollectionOperationStatus(status);
                 rv.set(cstatus.isSuccess(), cstatus);
                 if (!cstatus.isSuccess()) {
                   getLogger().debug(
-                          "Insertion to the collection failed : %s (type=%s, key=%s, subkey=%s, value=%s)",
+                          "Insertion to the collection failed : %s (type=%s, key=%s, elementKey=%s, value=%s)",
                           cstatus.getMessage(),
                           collectionInsert.getClass().getName(),
                           key,
-                          subkey,
+                          elementKey,
                           collectionInsert.getValue());
                 }
               }
@@ -910,27 +910,27 @@ public void complete() {
    * Public methods for collection items call this method.
    *
    * @param key             collection item's key
-   * @param subkey          element key (list index, b+tree bkey)
+   * @param elementKey      element key (list index, b+tree bkey)
    * @param collectionExist operation parameters (element value and so on)
    * @return future holding the success/failure of the operation
    */
-  private <T> CollectionFuture<Boolean> asyncCollectionExist(final String key, final String subkey,
+  private <T> CollectionFuture<Boolean> asyncCollectionExist(final String key, final String elementKey,
                                                              final CollectionExist collectionExist) {
     final CountDownLatch latch = new CountDownLatch(1);
     final CollectionFuture<Boolean> rv = new CollectionFuture<>(
             latch, operationTimeout);
-    Operation op = opFact.collectionExist(key, subkey, collectionExist,
+    Operation op = opFact.collectionExist(key, elementKey, collectionExist,
         new OperationCallback() {
           public void receivedStatus(OperationStatus status) {
             CollectionOperationStatus cstatus = toCollectionOperationStatus(status);
             boolean isExist = CollectionResponse.EXIST == cstatus.getResponse();
             rv.set(isExist, cstatus);
             if (!cstatus.isSuccess()) {
-              getLogger().debug("Exist command to the collection failed : %s (type=%s, key=%s, subkey=%s)",
+              getLogger().debug("Exist command to the collection failed : %s (type=%s, key=%s, elementKey=%s)",
                       cstatus.getMessage(),
                       collectionExist.getClass().getName(),
                       key,
-                      subkey);
+                      elementKey);
             }
           }
 
@@ -1986,13 +1986,13 @@ public <T> CollectionFuture<Boolean> asyncMopUpdate(String key, String mkey,
    * Public methods for collection items call this method.
    *
    * @param key              collection item's key
-   * @param subkey           element key (list index, b+tree bkey)
+   * @param elementKey       element key (list index, b+tree bkey)
    * @param collectionUpdate operation parameters (element value and so on)
    * @param tc               transcoder to serialize and unserialize value
    * @return future holding the success/failure of the operation
    */
   private <T> CollectionFuture<Boolean> asyncCollectionUpdate(
-          final String key, final String subkey,
+          final String key, final String elementKey,
           final CollectionUpdate<T> collectionUpdate, Transcoder<T> tc) {
 
     CachedData co = null;
@@ -2005,18 +2005,18 @@ private <T> CollectionFuture<Boolean> asyncCollectionUpdate(
     final CollectionFuture<Boolean> rv = new CollectionFuture<>(
             latch, operationTimeout);
 
-    Operation op = opFact.collectionUpdate(key, subkey, collectionUpdate,
+    Operation op = opFact.collectionUpdate(key, elementKey, collectionUpdate,
             ((co == null) ? null : co.getData()), new OperationCallback() {
               public void receivedStatus(OperationStatus status) {
                 CollectionOperationStatus cstatus = toCollectionOperationStatus(status);
                 rv.set(cstatus.isSuccess(), cstatus);
                 if (!cstatus.isSuccess()) {
                   getLogger().debug(
-                          "Insertion to the collection failed : %s (type=%s, key=%s, subkey=%s, value=%s)",
+                          "Insertion to the collection failed : %s (type=%s, key=%s, elementKey=%s, value=%s)",
                           cstatus.getMessage(),
                           collectionUpdate.getClass().getName(),
                           key,
-                          subkey,
+                          elementKey,
                           collectionUpdate.getNewValue());
                 }
               }
@@ -3233,18 +3233,18 @@ public CollectionFuture<Long> asyncBopDecr(String key, byte[] bkey,
    * Generic increment/decrement operation for b+tree items. Public methods call this method.
    *
    * @param k                b+tree item's key
-   * @param subkey           element key
+   * @param elementKey       element key
    * @param collectionMutate operation parameters (increment amount and so on)
    * @return future holding the incremented or decremented value
    */
-  private CollectionFuture<Long> asyncCollectionMutate(final String k, final String subkey,
+  private CollectionFuture<Long> asyncCollectionMutate(final String k, final String elementKey,
                                                        final CollectionMutate collectionMutate) {
 
     final CountDownLatch latch = new CountDownLatch(1);
 
     final CollectionFuture<Long> rv = new CollectionFuture<>(latch, operationTimeout);
 
-    Operation op = opFact.collectionMutate(k, subkey, collectionMutate,
+    Operation op = opFact.collectionMutate(k, elementKey, collectionMutate,
         new OperationCallback() {
 
           @Override
@@ -3256,14 +3256,14 @@ public void receivedStatus(OperationStatus status) {
               } catch (NumberFormatException e) {
                 rv.set(null, new CollectionOperationStatus(false, status.getMessage(), CollectionResponse.EXCEPTION));
 
-                getLogger().debug("Key(%s), Bkey(%s) Unknown response : %s", k, subkey, status);
+                getLogger().debug("Key(%s), Bkey(%s) Unknown response : %s", k, elementKey, status);
               }
               return;
             }
 
             rv.set(null, new CollectionOperationStatus(status));
 
-            getLogger().debug("Key(%s), Bkey(%s) Unknown response : %s", k, subkey, status);
+            getLogger().debug("Key(%s), Bkey(%s) Unknown response : %s", k, elementKey, status);
           }
 
           @Override
diff --git a/src/main/java/net/spy/memcached/OperationFactory.java b/src/main/java/net/spy/memcached/OperationFactory.java
index 7a64b6cb3..ec9b4583d 100644
--- a/src/main/java/net/spy/memcached/OperationFactory.java
+++ b/src/main/java/net/spy/memcached/OperationFactory.java
@@ -289,13 +289,13 @@ CASOperation cas(StoreType t, String key, long casId, int flags,
    * Insert operation for collection items.
    *
    * @param key              collection item's key
-   * @param subkey           element key (list index, b+tree bkey)
+   * @param elementKey       element key (list index, b+tree bkey)
    * @param collectionInsert operation parameters (value, eflags, attributes, and so on)
    * @param data             the serialized value
    * @param cb               the status callback
    * @return a new CollectionInsertOperation
    */
-  CollectionInsertOperation collectionInsert(String key, String subkey,
+  CollectionInsertOperation collectionInsert(String key, String elementKey,
                                              CollectionInsert<?> collectionInsert, byte[] data,
                                              OperationCallback cb);
 
@@ -339,12 +339,12 @@ CollectionDeleteOperation collectionDelete(String key,
    * Existence operation for collection items.
    *
    * @param key             collection item's key
-   * @param subkey          element key (list index, b+tree bkey)
+   * @param elementKey      element key (list index, b+tree bkey)
    * @param collectionExist operation parameters (element value and so on)
    * @param cb              the callback that will contain the results
    * @return a new CollectionExistOperation
    */
-  CollectionExistOperation collectionExist(String key, String subkey,
+  CollectionExistOperation collectionExist(String key, String elementKey,
                                            CollectionExist collectionExist, OperationCallback cb);
 
   /**
@@ -421,13 +421,13 @@ CollectionCountOperation collectionCount(String key,
    * Update operation for collection items.
    *
    * @param key              collection item's key
-   * @param subkey           element key (list index, b+tree bkey)
+   * @param elementKey       element key (list index, b+tree bkey)
    * @param collectionUpdate (element value and so on)
    * @param data             the serialized value
    * @param cb               the status callback
    * @return a new CollectionUpdateOperation
    */
-  CollectionUpdateOperation collectionUpdate(String key, String subkey,
+  CollectionUpdateOperation collectionUpdate(String key, String elementKey,
                                              CollectionUpdate<?> collectionUpdate, byte[] data,
                                              OperationCallback cb);
 
@@ -447,12 +447,12 @@ CollectionPipedUpdateOperation collectionPipedUpdate(String key,
    * Increment/Decrement operation for collection items (b+tree items).
    *
    * @param key              b+tree item's key
-   * @param subkey           element key
+   * @param elementKey       element key (b+tree bkey)
    * @param collectionMutate operation parameters (increment/decrement amount and so on)
    * @param cb               the callback that will contain the incremented/decremented result
    * @return a new CollectionMutateOperation
    */
-  CollectionMutateOperation collectionMutate(String key, String subkey,
+  CollectionMutateOperation collectionMutate(String key, String elementKey,
                                              CollectionMutate collectionMutate,
                                              OperationCallback cb);
 
diff --git a/src/main/java/net/spy/memcached/collection/BTreeFindPositionWithGet.java b/src/main/java/net/spy/memcached/collection/BTreeFindPositionWithGet.java
index ca7ba5baa..735cf67c5 100644
--- a/src/main/java/net/spy/memcached/collection/BTreeFindPositionWithGet.java
+++ b/src/main/java/net/spy/memcached/collection/BTreeFindPositionWithGet.java
@@ -106,11 +106,11 @@ public byte[] getAdditionalArgs() {
    */
   @Override
   public void decodeElemHeader(List<String> tokens) {
-    subkey = tokens.get(0);
-    if (subkey.startsWith("0x")) {
-      bkey =  new BKeyObject(BTreeUtil.hexStringToByteArrays(subkey.substring(2)));
+    elementKey = tokens.get(0);
+    if (elementKey.startsWith("0x")) {
+      bkey =  new BKeyObject(BTreeUtil.hexStringToByteArrays(elementKey.substring(2)));
     } else {
-      bkey = new BKeyObject(Long.parseLong(subkey));
+      bkey = new BKeyObject(Long.parseLong(elementKey));
     }
     if (tokens.size() == 2) {
       dataLength = Integer.parseInt(tokens.get(1));
diff --git a/src/main/java/net/spy/memcached/collection/BTreeGet.java b/src/main/java/net/spy/memcached/collection/BTreeGet.java
index 8729d8cad..2b643ad98 100644
--- a/src/main/java/net/spy/memcached/collection/BTreeGet.java
+++ b/src/main/java/net/spy/memcached/collection/BTreeGet.java
@@ -114,7 +114,7 @@ public byte[] getAdditionalArgs() {
 
   @Override
   public void decodeElemHeader(List<String> tokens) {
-    subkey = tokens.get(0);
+    elementKey = tokens.get(0);
     if (tokens.size() == 2) {
       dataLength = Integer.parseInt(tokens.get(1));
     } else {
diff --git a/src/main/java/net/spy/memcached/collection/BTreeGetByPosition.java b/src/main/java/net/spy/memcached/collection/BTreeGetByPosition.java
index 02373c70a..e75577338 100644
--- a/src/main/java/net/spy/memcached/collection/BTreeGetByPosition.java
+++ b/src/main/java/net/spy/memcached/collection/BTreeGetByPosition.java
@@ -99,11 +99,11 @@ public byte[] getAdditionalArgs() {
    */
   @Override
   public void decodeElemHeader(List<String> tokens) {
-    subkey = tokens.get(0);
-    if (subkey.startsWith("0x")) {
-      bkey =  new BKeyObject(BTreeUtil.hexStringToByteArrays(subkey.substring(2)));
+    elementKey = tokens.get(0);
+    if (elementKey.startsWith("0x")) {
+      bkey =  new BKeyObject(BTreeUtil.hexStringToByteArrays(elementKey.substring(2)));
     } else {
-      bkey = new BKeyObject(Long.parseLong(subkey));
+      bkey = new BKeyObject(Long.parseLong(elementKey));
     }
     if (tokens.size() == 2) {
       dataLength = Integer.parseInt(tokens.get(1));
diff --git a/src/main/java/net/spy/memcached/collection/BTreeInsertAndGet.java b/src/main/java/net/spy/memcached/collection/BTreeInsertAndGet.java
index 40cc5dafe..c69de142a 100644
--- a/src/main/java/net/spy/memcached/collection/BTreeInsertAndGet.java
+++ b/src/main/java/net/spy/memcached/collection/BTreeInsertAndGet.java
@@ -68,11 +68,11 @@ private BTreeInsertAndGet(BKeyObject bKey, byte[] eFlag, T value, boolean update
 
   @Override
   public void decodeElemHeader(List<String> tokens) {
-    subkey = tokens.get(0);
-    if (subkey.startsWith("0x")) {
-      bKey =  new BKeyObject(BTreeUtil.hexStringToByteArrays(subkey.substring(2)));
+    elementKey = tokens.get(0);
+    if (elementKey.startsWith("0x")) {
+      bKey =  new BKeyObject(BTreeUtil.hexStringToByteArrays(elementKey.substring(2)));
     } else {
-      bKey = new BKeyObject(Long.parseLong(subkey));
+      bKey = new BKeyObject(Long.parseLong(elementKey));
     }
     if (tokens.size() == 2) {
       dataLength = Integer.parseInt(tokens.get(1));
diff --git a/src/main/java/net/spy/memcached/collection/CollectionGet.java b/src/main/java/net/spy/memcached/collection/CollectionGet.java
index 6680d63d4..b93553d89 100644
--- a/src/main/java/net/spy/memcached/collection/CollectionGet.java
+++ b/src/main/java/net/spy/memcached/collection/CollectionGet.java
@@ -25,7 +25,7 @@ public abstract class CollectionGet {
 
   protected String range;
   protected String str;
-  protected String subkey;
+  protected String elementKey;
   protected int dataLength;
 
   protected byte[] elementFlag;
@@ -40,8 +40,8 @@ public boolean isDropIfEmpty() {
     return dropIfEmpty;
   }
 
-  public String getSubkey() {
-    return subkey;
+  public String getElementKey() {
+    return elementKey;
   }
 
   public int getDataLength() {
diff --git a/src/main/java/net/spy/memcached/collection/MapGet.java b/src/main/java/net/spy/memcached/collection/MapGet.java
index e8c7a954e..7c89b2812 100644
--- a/src/main/java/net/spy/memcached/collection/MapGet.java
+++ b/src/main/java/net/spy/memcached/collection/MapGet.java
@@ -98,7 +98,7 @@ public String getCommand() {
 
   @Override
   public void decodeElemHeader(List<String> tokens) {
-    this.subkey = tokens.get(0);
+    this.elementKey = tokens.get(0);
     this.dataLength = Integer.parseInt(tokens.get(1));
   }
 }
diff --git a/src/main/java/net/spy/memcached/ops/BaseOperationFactory.java b/src/main/java/net/spy/memcached/ops/BaseOperationFactory.java
index 3fc20215f..5cf494e74 100644
--- a/src/main/java/net/spy/memcached/ops/BaseOperationFactory.java
+++ b/src/main/java/net/spy/memcached/ops/BaseOperationFactory.java
@@ -93,7 +93,7 @@ public Collection<Operation> clone(KeyedOperation op) {
               (GetAttrOperation.Callback) c.getCallback()));
     } else if (op instanceof CollectionInsertOperation) {
       CollectionInsertOperation c = (CollectionInsertOperation) op;
-      rv.add(collectionInsert(first(c.getKeys()), c.getSubKey(),
+      rv.add(collectionInsert(first(c.getKeys()), c.getElementKey(),
               c.getInsert(), c.getData(), c.getCallback()));
     } else if (op instanceof CollectionGetOperation) {
       CollectionGetOperation c = (CollectionGetOperation) op;
@@ -105,7 +105,7 @@ public Collection<Operation> clone(KeyedOperation op) {
               c.getCallback()));
     } else if (op instanceof CollectionExistOperation) {
       CollectionExistOperation c = (CollectionExistOperation) op;
-      rv.add(collectionExist(first(c.getKeys()), c.getSubKey(),
+      rv.add(collectionExist(first(c.getKeys()), c.getElementKey(),
               c.getExist(), c.getCallback()));
     } else {
       assert false : "Unhandled operation type: " + op.getClass();
diff --git a/src/main/java/net/spy/memcached/ops/CollectionExistOperation.java b/src/main/java/net/spy/memcached/ops/CollectionExistOperation.java
index 1242b73e9..27c7ac7df 100644
--- a/src/main/java/net/spy/memcached/ops/CollectionExistOperation.java
+++ b/src/main/java/net/spy/memcached/ops/CollectionExistOperation.java
@@ -23,7 +23,7 @@
  */
 public interface CollectionExistOperation extends KeyedOperation {
 
-  String getSubKey();
+  String getElementKey();
 
   CollectionExist getExist();
 
diff --git a/src/main/java/net/spy/memcached/ops/CollectionGetOperation.java b/src/main/java/net/spy/memcached/ops/CollectionGetOperation.java
index f61706da3..c05ad54e0 100644
--- a/src/main/java/net/spy/memcached/ops/CollectionGetOperation.java
+++ b/src/main/java/net/spy/memcached/ops/CollectionGetOperation.java
@@ -26,6 +26,6 @@ public interface CollectionGetOperation extends KeyedOperation {
   CollectionGet getGet();
 
   interface Callback extends OperationCallback {
-    void gotData(String subkey, int flags, byte[] data, byte[] eflag);
+    void gotData(String elementKey, int flags, byte[] data, byte[] eflag);
   }
 }
diff --git a/src/main/java/net/spy/memcached/ops/CollectionInsertOperation.java b/src/main/java/net/spy/memcached/ops/CollectionInsertOperation.java
index 7abb1d05b..6794c7584 100644
--- a/src/main/java/net/spy/memcached/ops/CollectionInsertOperation.java
+++ b/src/main/java/net/spy/memcached/ops/CollectionInsertOperation.java
@@ -23,7 +23,7 @@
  */
 public interface CollectionInsertOperation extends KeyedOperation {
 
-  String getSubKey();
+  String getElementKey();
 
   CollectionInsert<?> getInsert();
 
diff --git a/src/main/java/net/spy/memcached/ops/CollectionUpdateOperation.java b/src/main/java/net/spy/memcached/ops/CollectionUpdateOperation.java
index b7bc0e700..d33d814cc 100644
--- a/src/main/java/net/spy/memcached/ops/CollectionUpdateOperation.java
+++ b/src/main/java/net/spy/memcached/ops/CollectionUpdateOperation.java
@@ -23,7 +23,7 @@
  */
 public interface CollectionUpdateOperation extends KeyedOperation {
 
-  String getSubKey();
+  String getElementKey();
 
   CollectionUpdate<?> getUpdate();
 
diff --git a/src/main/java/net/spy/memcached/protocol/ascii/AsciiOperationFactory.java b/src/main/java/net/spy/memcached/protocol/ascii/AsciiOperationFactory.java
index 5ea9e226b..71afc961f 100644
--- a/src/main/java/net/spy/memcached/protocol/ascii/AsciiOperationFactory.java
+++ b/src/main/java/net/spy/memcached/protocol/ascii/AsciiOperationFactory.java
@@ -196,10 +196,10 @@ public GetAttrOperation getAttr(String key, GetAttrOperation.Callback cb) {
   }
 
   @Override
-  public CollectionInsertOperation collectionInsert(String key, String subkey,
+  public CollectionInsertOperation collectionInsert(String key, String elementKey,
                                                     CollectionInsert<?> collectionInsert,
                                                     byte[] data, OperationCallback cb) {
-    return new CollectionInsertOperationImpl(key, subkey,
+    return new CollectionInsertOperationImpl(key, elementKey,
         collectionInsert, data, cb);
   }
 
@@ -225,10 +225,10 @@ public CollectionDeleteOperation collectionDelete(String key,
   }
 
   @Override
-  public CollectionExistOperation collectionExist(String key, String subkey,
+  public CollectionExistOperation collectionExist(String key, String elementKey,
                                                   CollectionExist collectionExist,
                                                   OperationCallback cb) {
-    return new CollectionExistOperationImpl(key, subkey, collectionExist, cb);
+    return new CollectionExistOperationImpl(key, elementKey, collectionExist, cb);
   }
 
   @Override
@@ -258,11 +258,11 @@ public BTreeSortMergeGetOperation bopsmget(BTreeSMGet<?> smGet,
 
   @Override
   public CollectionUpdateOperation collectionUpdate(String key,
-                                                    String subkey,
+                                                    String elementKey,
                                                     CollectionUpdate<?> collectionUpdate,
                                                     byte[] data,
                                                     OperationCallback cb) {
-    return new CollectionUpdateOperationImpl(key, subkey, collectionUpdate,
+    return new CollectionUpdateOperationImpl(key, elementKey, collectionUpdate,
         data, cb);
   }
 
@@ -294,10 +294,10 @@ public BTreeGetBulkOperation bopGetBulk(BTreeGetBulk<?> getBulk,
 
   @Override
   public CollectionMutateOperation collectionMutate(String key,
-                                                    String subkey,
+                                                    String elementKey,
                                                     CollectionMutate collectionMutate,
                                                     OperationCallback cb) {
-    return new CollectionMutateOperationImpl(key, subkey, collectionMutate, cb);
+    return new CollectionMutateOperationImpl(key, elementKey, collectionMutate, cb);
   }
 
   @Override
diff --git a/src/main/java/net/spy/memcached/protocol/ascii/CollectionExistOperationImpl.java b/src/main/java/net/spy/memcached/protocol/ascii/CollectionExistOperationImpl.java
index ed008d3b7..745992125 100644
--- a/src/main/java/net/spy/memcached/protocol/ascii/CollectionExistOperationImpl.java
+++ b/src/main/java/net/spy/memcached/protocol/ascii/CollectionExistOperationImpl.java
@@ -54,14 +54,14 @@ public final class CollectionExistOperationImpl extends OperationImpl
           false, "UNREADABLE", CollectionResponse.UNREADABLE);
 
   private final String key;
-  private final String subkey;
+  private final String elementKey;
   private final CollectionExist collectionExist;
 
-  public CollectionExistOperationImpl(String key, String subkey,
+  public CollectionExistOperationImpl(String key, String elementKey,
                                       CollectionExist collectionExist, OperationCallback cb) {
     super(cb);
     this.key = key;
-    this.subkey = subkey;
+    this.elementKey = elementKey;
     this.collectionExist = collectionExist;
     if (this.collectionExist instanceof SetExist) {
       setAPIType(APIType.SOP_EXIST);
@@ -91,10 +91,10 @@ public void initialize() {
     byte[] additionalArgs = collectionExist.getAdditionalArgs();
     ByteBuffer bb = ByteBuffer.allocate((null == additionalArgs ? 0 : additionalArgs.length)
             + KeyUtil.getKeyBytes(key).length
-            + KeyUtil.getKeyBytes(subkey).length
+            + KeyUtil.getKeyBytes(elementKey).length
             + args.length()
             + OVERHEAD);
-    setArguments(bb, collectionExist.getCommand(), key, subkey, args);
+    setArguments(bb, collectionExist.getCommand(), key, elementKey, args);
 
     if (null != additionalArgs) {
       bb.put(additionalArgs);
@@ -114,8 +114,8 @@ public Collection<String> getKeys() {
     return Collections.singleton(key);
   }
 
-  public String getSubKey() {
-    return subkey;
+  public String getElementKey() {
+    return elementKey;
   }
 
   public CollectionExist getExist() {
diff --git a/src/main/java/net/spy/memcached/protocol/ascii/CollectionGetOperationImpl.java b/src/main/java/net/spy/memcached/protocol/ascii/CollectionGetOperationImpl.java
index 0dd944aae..1da003212 100644
--- a/src/main/java/net/spy/memcached/protocol/ascii/CollectionGetOperationImpl.java
+++ b/src/main/java/net/spy/memcached/protocol/ascii/CollectionGetOperationImpl.java
@@ -213,7 +213,7 @@ public void handleRead(ByteBuffer bb) {
     if (lookingFor == '\0' && readOffset == data.length) {
       CollectionGetOperation.Callback cb =
               (CollectionGetOperation.Callback) getCallback();
-      cb.gotData(collectionGet.getSubkey(), flags, data, collectionGet.getElementFlag());
+      cb.gotData(collectionGet.getElementKey(), flags, data, collectionGet.getElementFlag());
       lookingFor = '\r';
     }
 
diff --git a/src/main/java/net/spy/memcached/protocol/ascii/CollectionInsertOperationImpl.java b/src/main/java/net/spy/memcached/protocol/ascii/CollectionInsertOperationImpl.java
index e445eae6e..af88f65c9 100644
--- a/src/main/java/net/spy/memcached/protocol/ascii/CollectionInsertOperationImpl.java
+++ b/src/main/java/net/spy/memcached/protocol/ascii/CollectionInsertOperationImpl.java
@@ -67,16 +67,16 @@ public final class CollectionInsertOperationImpl extends OperationImpl
           false, "BKEY_MISMATCH", CollectionResponse.BKEY_MISMATCH);
 
   private final String key;
-  private final String subkey;    // e.g.) 0 or 0x00
+  private final String elementKey;    // e.g.) 0 or 0x00
   private final CollectionInsert<?> collectionInsert;
   private final byte[] data;
 
-  public CollectionInsertOperationImpl(String key, String subkey,
+  public CollectionInsertOperationImpl(String key, String elementKey,
                                        CollectionInsert<?> collectionInsert, byte[] data,
                                        OperationCallback cb) {
     super(cb);
     this.key = key;
-    this.subkey = subkey;
+    this.elementKey = elementKey;
     this.collectionInsert = collectionInsert;
     this.data = data;
     if (this.collectionInsert instanceof ListInsert) {
@@ -124,11 +124,11 @@ public void initialize() {
     String args = collectionInsert.stringify();
     ByteBuffer bb = ByteBuffer.allocate(data.length
             + KeyUtil.getKeyBytes(key).length
-            + KeyUtil.getKeyBytes(subkey).length
+            + KeyUtil.getKeyBytes(elementKey).length
             + KeyUtil.getKeyBytes(collectionInsert.getElementFlagByHex()).length
             + args.length()
             + OVERHEAD);
-    setArguments(bb, collectionInsert.getCommand(), key, subkey,
+    setArguments(bb, collectionInsert.getCommand(), key, elementKey,
             collectionInsert.getElementFlagByHex(), data.length, args);
     bb.put(data);
     bb.put(CRLF);
@@ -145,8 +145,8 @@ public Collection<String> getKeys() {
     return Collections.singleton(key);
   }
 
-  public String getSubKey() {
-    return subkey;
+  public String getElementKey() {
+    return elementKey;
   }
 
   public CollectionInsert<?> getInsert() {
diff --git a/src/main/java/net/spy/memcached/protocol/ascii/CollectionMutateOperationImpl.java b/src/main/java/net/spy/memcached/protocol/ascii/CollectionMutateOperationImpl.java
index d2f4f4397..ae889d480 100644
--- a/src/main/java/net/spy/memcached/protocol/ascii/CollectionMutateOperationImpl.java
+++ b/src/main/java/net/spy/memcached/protocol/ascii/CollectionMutateOperationImpl.java
@@ -57,14 +57,14 @@ public final class CollectionMutateOperationImpl extends OperationImpl implement
           false, "OUT_OF_RANGE", CollectionResponse.OUT_OF_RANGE);
 
   private final String key;
-  private final String subkey;
+  private final String elementKey;
   private final CollectionMutate collectionMutate;
 
-  public CollectionMutateOperationImpl(String key, String subkey,
+  public CollectionMutateOperationImpl(String key, String elementKey,
                                        CollectionMutate collectionMutate, OperationCallback cb) {
     super(cb);
     this.key = key;
-    this.subkey = subkey;
+    this.elementKey = elementKey;
     this.collectionMutate = collectionMutate;
     if (this.collectionMutate instanceof BTreeMutate) {
       if (((BTreeMutate) this.collectionMutate).getMutator() == Mutator.incr) {
@@ -111,10 +111,10 @@ public void initialize() {
     String cmd = collectionMutate.getCommand();
     String args = collectionMutate.stringify();
     ByteBuffer bb = ByteBuffer.allocate(KeyUtil.getKeyBytes(key).length
-            + KeyUtil.getKeyBytes(subkey).length
+            + KeyUtil.getKeyBytes(elementKey).length
             + cmd.length() + args.length() + 16);
 
-    setArguments(bb, cmd, key, subkey, args);
+    setArguments(bb, cmd, key, elementKey, args);
     ((Buffer) bb).flip();
     setBuffer(bb);
 
@@ -128,8 +128,8 @@ public Collection<String> getKeys() {
     return Collections.singleton(key);
   }
 
-  public String getSubKey() {
-    return subkey;
+  public String getElementKey() {
+    return elementKey;
   }
 
   @Override
diff --git a/src/main/java/net/spy/memcached/protocol/ascii/CollectionUpdateOperationImpl.java b/src/main/java/net/spy/memcached/protocol/ascii/CollectionUpdateOperationImpl.java
index e4f9da1cd..74524a040 100644
--- a/src/main/java/net/spy/memcached/protocol/ascii/CollectionUpdateOperationImpl.java
+++ b/src/main/java/net/spy/memcached/protocol/ascii/CollectionUpdateOperationImpl.java
@@ -60,16 +60,16 @@ public final class CollectionUpdateOperationImpl extends OperationImpl implement
           false, "EFLAG_MISMATCH", CollectionResponse.EFLAG_MISMATCH);
 
   private final String key;
-  private final String subkey; // e.g.) 0 or 0x00
+  private final String elementKey; // e.g.) 0 or 0x00
   private final CollectionUpdate<?> collectionUpdate;
   private final byte[] data;
 
-  public CollectionUpdateOperationImpl(String key, String subkey,
+  public CollectionUpdateOperationImpl(String key, String elementKey,
                                        CollectionUpdate<?> collectionUpdate, byte[] data,
                                        OperationCallback cb) {
     super(cb);
     this.key = key;
-    this.subkey = subkey;
+    this.elementKey = elementKey;
     this.collectionUpdate = collectionUpdate;
     this.data = data;
     if (this.collectionUpdate instanceof BTreeUpdate) {
@@ -121,11 +121,11 @@ public void initialize() {
     ByteBuffer bb = ByteBuffer
             .allocate(((data != null) ? data.length : 0)
                     + KeyUtil.getKeyBytes(key).length
-                    + KeyUtil.getKeyBytes(subkey).length
+                    + KeyUtil.getKeyBytes(elementKey).length
                     + eflagStr.length() + args.length()
                     + OVERHEAD);
 
-    setArguments(bb, collectionUpdate.getCommand(), key, subkey,
+    setArguments(bb, collectionUpdate.getCommand(), key, elementKey,
             eflagStr, (data != null ? data.length : "-1"), args);
 
     if (data != null) {
@@ -146,8 +146,8 @@ public Collection<String> getKeys() {
     return Collections.singleton(key);
   }
 
-  public String getSubKey() {
-    return subkey;
+  public String getElementKey() {
+    return elementKey;
   }
 
   public CollectionUpdate<?> getUpdate() {
diff --git a/src/main/java/net/spy/memcached/protocol/binary/BinaryOperationFactory.java b/src/main/java/net/spy/memcached/protocol/binary/BinaryOperationFactory.java
index 361442cb8..2fde05eb7 100644
--- a/src/main/java/net/spy/memcached/protocol/binary/BinaryOperationFactory.java
+++ b/src/main/java/net/spy/memcached/protocol/binary/BinaryOperationFactory.java
@@ -219,7 +219,7 @@ public GetAttrOperation getAttr(String key,
   }
 
   @Override
-  public CollectionInsertOperation collectionInsert(String key, String subkey,
+  public CollectionInsertOperation collectionInsert(String key, String elementKey,
                                                     CollectionInsert<?> collectionInsert,
                                                     byte[] data,
                                                     OperationCallback cb) {
@@ -252,7 +252,7 @@ public CollectionDeleteOperation collectionDelete(String key,
   }
 
   @Override
-  public CollectionExistOperation collectionExist(String key, String subkey,
+  public CollectionExistOperation collectionExist(String key, String elementKey,
                                                   CollectionExist collectionExist,
                                                   OperationCallback cb) {
     throw new RuntimeException(
@@ -290,7 +290,7 @@ public BTreeSortMergeGetOperation bopsmget(BTreeSMGet<?> smGet,
 
   @Override
   public CollectionUpdateOperation collectionUpdate(String key,
-                                                    String subkey,
+                                                    String elementKey,
                                                     CollectionUpdate<?> collectionUpdate,
                                                     byte[] data,
                                                     OperationCallback cb) {
@@ -308,7 +308,7 @@ public CollectionPipedUpdateOperation collectionPipedUpdate(String key,
 
   @Override
   public CollectionMutateOperation collectionMutate(String key,
-                                                    String subkey,
+                                                    String elementKey,
                                                     CollectionMutate collectionMutate,
                                                     OperationCallback cb) {
     throw new RuntimeException(
diff --git a/src/main/java/net/spy/memcached/v2/AsyncArcusCommands.java b/src/main/java/net/spy/memcached/v2/AsyncArcusCommands.java
index 9cd98846f..d10d23303 100644
--- a/src/main/java/net/spy/memcached/v2/AsyncArcusCommands.java
+++ b/src/main/java/net/spy/memcached/v2/AsyncArcusCommands.java
@@ -770,7 +770,7 @@ public void complete() {
       }
 
       @Override
-      public void gotData(String subKey, int flags, byte[] data, byte[] eFlag) {
+      public void gotData(String elementKey, int flags, byte[] data, byte[] eFlag) {
         result.set(new CachedData(flags, data, tcForCollection.getMaxSize()));
       }
     };
@@ -815,7 +815,7 @@ public void complete() {
       }
 
       @Override
-      public void gotData(String subKey, int flags, byte[] data, byte[] eFlag) {
+      public void gotData(String elementKey, int flags, byte[] data, byte[] eFlag) {
         result.get().add(new CachedData(flags, data, tcForCollection.getMaxSize()));
       }
     };
@@ -870,7 +870,7 @@ public ArcusFuture<Set<T>> sopGet(String key, int count, GetMode mode) {
 
     CollectionGetOperation.Callback cb = new CollectionGetOperation.Callback() {
       @Override
-      public void gotData(String subKey, int flags, byte[] data, byte[] eFlag) {
+      public void gotData(String elementKey, int flags, byte[] data, byte[] eFlag) {
         result.get().add(new CachedData(flags, data, tcForCollection.getMaxSize()));
       }
 
diff --git a/src/test/manual/net/spy/memcached/MultibyteKeyTest.java b/src/test/manual/net/spy/memcached/MultibyteKeyTest.java
index 6134c7957..19efee07a 100644
--- a/src/test/manual/net/spy/memcached/MultibyteKeyTest.java
+++ b/src/test/manual/net/spy/memcached/MultibyteKeyTest.java
@@ -163,7 +163,7 @@ public void decodeElemHeader(List<String> tokens) {
         }
       }, new CollectionGetOperation.Callback() {
         @Override
-        public void gotData(String subkey, int flags, byte[] data, byte[] eflag) {
+        public void gotData(String elementKey, int flags, byte[] data, byte[] eflag) {
         }
 
         @Override