diff --git a/x-pack/legacy/plugins/maps/public/layers/sources/es_agg_source.js b/x-pack/legacy/plugins/maps/public/layers/sources/es_agg_source.js
index fd3ae8f0ab7e3..967a3c41aec26 100644
--- a/x-pack/legacy/plugins/maps/public/layers/sources/es_agg_source.js
+++ b/x-pack/legacy/plugins/maps/public/layers/sources/es_agg_source.js
@@ -15,7 +15,7 @@ import {
   FIELD_ORIGIN,
 } from '../../../common/constants';
 
-const AGG_DELIMITER = '_of_';
+export const AGG_DELIMITER = '_of_';
 
 export class AbstractESAggSource extends AbstractESSource {
   static METRIC_SCHEMA_CONFIG = {
@@ -53,33 +53,12 @@ export class AbstractESAggSource extends AbstractESSource {
       : [];
   }
 
-  createField({ fieldName, label }) {
-    //if there is a corresponding field with a custom label, use that one.
-    if (!label) {
-      const matchField = this._metricFields.find(field => field.getName() === fieldName);
-      if (matchField) {
-        label = matchField.getLabel();
-      }
-    }
+  getFieldByName(name) {
+    return this.getMetricFieldForName(name);
+  }
 
-    if (fieldName === COUNT_PROP_NAME) {
-      return new ESAggMetricField({
-        aggType: COUNT_AGG_TYPE,
-        label: label,
-        source: this,
-        origin: this.getOriginForField(),
-      });
-    }
-    //this only works because aggType is a fixed set and does not include the `_of_` string
-    const [aggType, docField] = fieldName.split(AGG_DELIMITER);
-    const esDocField = new ESDocField({ fieldName: docField, source: this });
-    return new ESAggMetricField({
-      label: label,
-      esDocField,
-      aggType,
-      source: this,
-      origin: this.getOriginForField(),
-    });
+  createField() {
+    throw new Error('Cannot create a new field from just a fieldname for an es_agg_source.');
   }
 
   hasMatchingMetricField(fieldName) {
diff --git a/x-pack/legacy/plugins/maps/public/layers/sources/es_term_source.js b/x-pack/legacy/plugins/maps/public/layers/sources/es_term_source.js
index 6e8b2e1e7c6f5..443668984b0b4 100644
--- a/x-pack/legacy/plugins/maps/public/layers/sources/es_term_source.js
+++ b/x-pack/legacy/plugins/maps/public/layers/sources/es_term_source.js
@@ -9,9 +9,14 @@ import _ from 'lodash';
 import { Schemas } from 'ui/vis/editors/default/schemas';
 import { AggConfigs } from 'ui/agg_types';
 import { i18n } from '@kbn/i18n';
-import { DEFAULT_MAX_BUCKETS_LIMIT, FIELD_ORIGIN, METRIC_TYPE } from '../../../common/constants';
+import {
+  COUNT_PROP_LABEL,
+  DEFAULT_MAX_BUCKETS_LIMIT,
+  FIELD_ORIGIN,
+  METRIC_TYPE,
+} from '../../../common/constants';
 import { ESDocField } from '../fields/es_doc_field';
-import { AbstractESAggSource } from './es_agg_source';
+import { AbstractESAggSource, AGG_DELIMITER } from './es_agg_source';
 
 const TERMS_AGG_NAME = 'join';
 
@@ -85,14 +90,15 @@ export class ESTermSource extends AbstractESAggSource {
   }
 
   formatMetricKey(aggType, fieldName) {
-    const metricKey = aggType !== METRIC_TYPE.COUNT ? `${aggType}_of_${fieldName}` : aggType;
+    const metricKey =
+      aggType !== METRIC_TYPE.COUNT ? `${aggType}${AGG_DELIMITER}${fieldName}` : aggType;
     return `${FIELD_NAME_PREFIX}${metricKey}${GROUP_BY_DELIMITER}${
       this._descriptor.indexPatternTitle
     }.${this._termField.getName()}`;
   }
 
   formatMetricLabel(type, fieldName) {
-    const metricLabel = type !== METRIC_TYPE.COUNT ? `${type} ${fieldName}` : 'count';
+    const metricLabel = type !== METRIC_TYPE.COUNT ? `${type} ${fieldName}` : COUNT_PROP_LABEL;
     return `${metricLabel} of ${this._descriptor.indexPatternTitle}:${this._termField.getName()}`;
   }
 
diff --git a/x-pack/legacy/plugins/maps/public/layers/sources/vector_source.js b/x-pack/legacy/plugins/maps/public/layers/sources/vector_source.js
index b9d8ae86c5850..3952aacf03b33 100644
--- a/x-pack/legacy/plugins/maps/public/layers/sources/vector_source.js
+++ b/x-pack/legacy/plugins/maps/public/layers/sources/vector_source.js
@@ -50,10 +50,26 @@ export class AbstractVectorSource extends AbstractSource {
     );
   }
 
+  /**
+   * factory function creating a new field-instance
+   * @param fieldName
+   * @param label
+   * @returns {ESAggMetricField}
+   */
   createField() {
     throw new Error(`Should implemement ${this.constructor.type} ${this}`);
   }
 
+  /**
+   * Retrieves a field. This may be an existing instance.
+   * @param fieldName
+   * @param label
+   * @returns {ESAggMetricField}
+   */
+  getFieldByName(name) {
+    return this.createField({ fieldName: name });
+  }
+
   _createDefaultLayerDescriptor(options, mapColors) {
     return VectorLayer.createDescriptor(
       {
diff --git a/x-pack/legacy/plugins/maps/public/layers/styles/vector/vector_style.js b/x-pack/legacy/plugins/maps/public/layers/styles/vector/vector_style.js
index 30d1c5726ba48..ec0afb6a6a37e 100644
--- a/x-pack/legacy/plugins/maps/public/layers/styles/vector/vector_style.js
+++ b/x-pack/legacy/plugins/maps/public/layers/styles/vector/vector_style.js
@@ -579,9 +579,7 @@ export class VectorStyle extends AbstractStyle {
     //fieldDescriptor.label is ignored. This is essentially cruft duplicating label-info from the metric-selection
     //Ignore this custom label
     if (fieldDescriptor.origin === FIELD_ORIGIN.SOURCE) {
-      return this._source.createField({
-        fieldName: fieldDescriptor.name,
-      });
+      return this._source.getFieldByName(fieldDescriptor.name);
     } else if (fieldDescriptor.origin === FIELD_ORIGIN.JOIN) {
       const join = this._layer.getValidJoins().find(join => {
         return join.getRightJoinSource().hasMatchingMetricField(fieldDescriptor.name);
diff --git a/x-pack/legacy/plugins/maps/public/layers/styles/vector/vector_style.test.js b/x-pack/legacy/plugins/maps/public/layers/styles/vector/vector_style.test.js
index c250d83720580..b8f5c74139a63 100644
--- a/x-pack/legacy/plugins/maps/public/layers/styles/vector/vector_style.test.js
+++ b/x-pack/legacy/plugins/maps/public/layers/styles/vector/vector_style.test.js
@@ -30,6 +30,9 @@ class MockSource {
   getSupportedShapeTypes() {
     return this._supportedShapeTypes;
   }
+  getFieldByName(fieldName) {
+    return new MockField({ fieldName });
+  }
   createField({ fieldName }) {
     return new MockField({ fieldName });
   }