diff --git a/integ-test/src/yamlRestTest/resources/rest-api-spec/test/issues/4481.yml b/integ-test/src/yamlRestTest/resources/rest-api-spec/test/issues/4481.yml
new file mode 100644
index 00000000000..5dceb720c3b
--- /dev/null
+++ b/integ-test/src/yamlRestTest/resources/rest-api-spec/test/issues/4481.yml
@@ -0,0 +1,59 @@
+"Fix missing keywordsCanBeID":
+  - skip:
+      features:
+        - headers
+        - allowed_warnings
+  - do:
+      indices.create:
+        index: log-test
+        body:
+          mappings:
+            properties:
+              "as":
+                properties:
+                  "field":
+                    properties:
+                      "on":
+                        properties:
+                          "limit":
+                            properties:
+                              "datamodel":
+                                properties:
+                                  "overwrite":
+                                    properties:
+                                      "sed":
+                                        properties:
+                                          "label":
+                                            properties:
+                                              "aggregation":
+                                                properties:
+                                                  "brain":
+                                                    properties:
+                                                      "simple_pattern":
+                                                        properties:
+                                                          "max_match":
+                                                            properties:
+                                                              "offset_field":
+                                                                properties:
+                                                                  "to":
+                                                                    properties:
+                                                                      "millisecond":
+                                                                        type: integer
+
+  - do:
+      bulk:
+        index: log-test
+        refresh: true
+        body:
+          - '{"index": {}}'
+          - '{"as": {"field": {"on": {"limit": {"datamodel": {"overwrite": {"sed": {"label": {"aggregation": {"brain": {"simple_pattern": {"max_match": {"offset_field": {"to": {"millisecond": 1 } } } } } } } } } } } } } } }'
+
+  - do:
+      headers:
+        Content-Type: 'application/json'
+      ppl:
+        body:
+          query: source=log-test | fields as.field.on.limit.datamodel.overwrite.sed.label.aggregation.brain.simple_pattern.max_match.offset_field.to.millisecond
+
+  - match: { total: 1 }
+  - length: { datarows: 1 }
diff --git a/ppl/src/main/antlr/OpenSearchPPLLexer.g4 b/ppl/src/main/antlr/OpenSearchPPLLexer.g4
index 30ba0f7013d..ba1e4960bb2 100644
--- a/ppl/src/main/antlr/OpenSearchPPLLexer.g4
+++ b/ppl/src/main/antlr/OpenSearchPPLLexer.g4
@@ -170,7 +170,6 @@ HOUR_OF_DAY:                        'HOUR_OF_DAY';
 HOUR_SECOND:                        'HOUR_SECOND';
 INTERVAL:                           'INTERVAL';
 MICROSECOND:                        'MICROSECOND';
-MILLISECOND:                        'MILLISECOND';
 MINUTE:                             'MINUTE';
 MINUTE_MICROSECOND:                 'MINUTE_MICROSECOND';
 MINUTE_OF_DAY:                      'MINUTE_OF_DAY';
@@ -188,9 +187,7 @@ YEAR:                               'YEAR';
 YEAR_MONTH:                         'YEAR_MONTH';
 
 // DATASET TYPES
-DATAMODEL:                          'DATAMODEL';
 LOOKUP:                             'LOOKUP';
-SAVEDSEARCH:                        'SAVEDSEARCH';
 
 // CONVERTED DATA TYPES
 INT:                                'INT';
@@ -398,7 +395,6 @@ SUBSTRING:                          'SUBSTRING';
 LTRIM:                              'LTRIM';
 RTRIM:                              'RTRIM';
 TRIM:                               'TRIM';
-TO:                                 'TO';
 LOWER:                              'LOWER';
 UPPER:                              'UPPER';
 CONCAT:                             'CONCAT';
diff --git a/ppl/src/main/antlr/OpenSearchPPLParser.g4 b/ppl/src/main/antlr/OpenSearchPPLParser.g4
index 4cfa1288de7..2e03314c5f7 100644
--- a/ppl/src/main/antlr/OpenSearchPPLParser.g4
+++ b/ppl/src/main/antlr/OpenSearchPPLParser.g4
@@ -1467,7 +1467,16 @@ searchableKeyWord
    | PATH
    | INPUT
    | OUTPUT
-
+   | AS
+   | ON
+   | LIMIT
+   | OVERWRITE
+   | FIELD
+   | SED
+   | MAX_MATCH
+   | OFFSET_FIELD
+   | patternMethod
+   | patternMode
    // AGGREGATIONS AND WINDOW
    | statsFunctionName
    | windowFunctionName