diff --git a/modules/mapper-extras/src/main/java/org/elasticsearch/index/mapper/extras/MatchOnlyTextFieldMapper.java b/modules/mapper-extras/src/main/java/org/elasticsearch/index/mapper/extras/MatchOnlyTextFieldMapper.java
index b103a23772a47..055f6091ac484 100644
--- a/modules/mapper-extras/src/main/java/org/elasticsearch/index/mapper/extras/MatchOnlyTextFieldMapper.java
+++ b/modules/mapper-extras/src/main/java/org/elasticsearch/index/mapper/extras/MatchOnlyTextFieldMapper.java
@@ -157,6 +157,7 @@ public static class MatchOnlyTextFieldType extends StringFieldType {
 
         private final Analyzer indexAnalyzer;
         private final TextFieldType textFieldType;
+        private final String originalName;
 
         public MatchOnlyTextFieldType(
             String name,
@@ -168,6 +169,7 @@ public MatchOnlyTextFieldType(
             super(name, true, false, false, tsi, meta);
             this.indexAnalyzer = Objects.requireNonNull(indexAnalyzer);
             this.textFieldType = new TextFieldType(name, isSyntheticSource);
+            this.originalName = isSyntheticSource ? name() + "._original" : null;
         }
 
         public MatchOnlyTextFieldType(String name) {
@@ -394,7 +396,7 @@ protected BytesRef storedToBytesRef(Object stored) {
         }
 
         private String storedFieldNameForSyntheticSource() {
-            return name() + "._original";
+            return originalName;
         }
     }
 
diff --git a/server/src/main/java/org/elasticsearch/index/mapper/FieldArrayContext.java b/server/src/main/java/org/elasticsearch/index/mapper/FieldArrayContext.java
index ca293be5f511a..f818b34d6c9bb 100644
--- a/server/src/main/java/org/elasticsearch/index/mapper/FieldArrayContext.java
+++ b/server/src/main/java/org/elasticsearch/index/mapper/FieldArrayContext.java
@@ -63,7 +63,8 @@ void addToLuceneDocument(DocumentParserContext context) throws IOException {
                 offsetToOrd[nullOffset] = -1;
             }
 
-            try (var streamOutput = new BytesStreamOutput()) {
+            int expectedSize = offsetToOrd.length + 1; // Initialize buffer to avoid unnecessary resizing, assume 1 byte per offset + size.
+            try (var streamOutput = new BytesStreamOutput(expectedSize)) {
                 // Could just use vint for array length, but this allows for decoding my_field: null as -1
                 streamOutput.writeVInt(BitUtil.zigZagEncode(offsetToOrd.length));
                 for (int ord : offsetToOrd) {
diff --git a/server/src/main/java/org/elasticsearch/index/mapper/KeywordFieldMapper.java b/server/src/main/java/org/elasticsearch/index/mapper/KeywordFieldMapper.java
index b7e8e13e16839..127024f17a222 100644
--- a/server/src/main/java/org/elasticsearch/index/mapper/KeywordFieldMapper.java
+++ b/server/src/main/java/org/elasticsearch/index/mapper/KeywordFieldMapper.java
@@ -1058,6 +1058,7 @@ public boolean hasDocValuesSkipper() {
     private final boolean useDocValuesSkipper;
     private final String offsetsFieldName;
     private final SourceKeepMode indexSourceKeepMode;
+    private final String originalName;
 
     private KeywordFieldMapper(
         String simpleName,
@@ -1089,6 +1090,7 @@ private KeywordFieldMapper(
         this.useDocValuesSkipper = useDocValuesSkipper;
         this.offsetsFieldName = offsetsFieldName;
         this.indexSourceKeepMode = indexSourceKeepMode;
+        this.originalName = isSyntheticSource ? fullPath() + "._original" : null;
     }
 
     @Override
@@ -1255,7 +1257,7 @@ boolean hasNormalizer() {
      * for synthetic source.
      */
     private String originalName() {
-        return fullPath() + "._original";
+        return originalName;
     }
 
     @Override
diff --git a/x-pack/plugin/wildcard/src/main/java/org/elasticsearch/xpack/wildcard/mapper/WildcardFieldMapper.java b/x-pack/plugin/wildcard/src/main/java/org/elasticsearch/xpack/wildcard/mapper/WildcardFieldMapper.java
index 3e374cab327d3..77e275555deb4 100644
--- a/x-pack/plugin/wildcard/src/main/java/org/elasticsearch/xpack/wildcard/mapper/WildcardFieldMapper.java
+++ b/x-pack/plugin/wildcard/src/main/java/org/elasticsearch/xpack/wildcard/mapper/WildcardFieldMapper.java
@@ -896,6 +896,7 @@ protected String parseSourceValue(Object value) {
     private final int ignoreAbove;
     private final int ignoreAboveDefault;
     private final boolean storeIgnored;
+    private final String originalName;
 
     private WildcardFieldMapper(
         String simpleName,
@@ -911,6 +912,7 @@ private WildcardFieldMapper(
         this.indexVersionCreated = indexVersionCreated;
         this.ignoreAbove = builder.ignoreAbove.getValue();
         this.ignoreAboveDefault = builder.ignoreAboveDefault;
+        this.originalName = storeIgnored ? fullPath() + "._original" : null;
     }
 
     @Override
@@ -956,7 +958,7 @@ protected void parseCreateField(DocumentParserContext context) throws IOExceptio
     }
 
     private String originalName() {
-        return fullPath() + "._original";
+        return originalName;
     }
 
     void createFields(String value, LuceneDocument parseDoc, List<IndexableField> fields) {