diff --git a/x-pack/plugins/observability/public/components/custom_threshold/components/rule_condition_chart/painless_tinymath_parser.test.ts b/x-pack/plugins/observability/public/components/custom_threshold/components/rule_condition_chart/painless_tinymath_parser.test.ts
index bfc8cb955a2b8..a957c58167403 100644
--- a/x-pack/plugins/observability/public/components/custom_threshold/components/rule_condition_chart/painless_tinymath_parser.test.ts
+++ b/x-pack/plugins/observability/public/components/custom_threshold/components/rule_condition_chart/painless_tinymath_parser.test.ts
@@ -23,6 +23,16 @@ describe('PainlessTinyMathParser', () => {
     // ✅ checked with Lens Formula editor
     expect(parser.parse()).toEqual('100*average(system.cpu.system.pct)');
   });
+  it('should parse a simple equation with multi-char aggregation name', () => {
+    const equation = '100 * ABC-abc';
+    const parser = new PainlessTinyMathParser({
+      equation,
+      aggMap: {
+        'ABC-abc': 'average(system.cpu.system.pct)',
+      },
+    });
+    expect(parser.parse()).toEqual('100*average(system.cpu.system.pct)');
+  });
   it('should parse a simple equation with two aggregations A and B', () => {
     const equation = '100 * A + B / 100';
     const parser = new PainlessTinyMathParser({
@@ -162,6 +172,20 @@ describe('PainlessTinyMathParser', () => {
       'ifelse(ifelse(average(system.cpu.system.pct)>0,0,1) + ifelse(average(system.cpu.user.pct)==10,0,1) * ifelse(average(system.cpu.system.pct)<200,0,1) + ifelse(average(system.cpu.user.pct)==2,1,0) > 0, 100, ifelse(average(system.cpu.system.pct)==10, 200, 300))'
     );
   });
+  it('should parse a complex equation with multi char aggregation name', () => {
+    const equation =
+      '!(aa > 0) || baa !== 10 && !(aa < 200 || baa == 2) ? 100 : aa == 10 ? 200 : 300';
+    const parser = new PainlessTinyMathParser({
+      equation,
+      aggMap: {
+        aa: 'average(system.cpu.system.pct)',
+        baa: 'average(system.cpu.user.pct)',
+      },
+    });
+    expect(parser.parse()).toEqual(
+      'ifelse(ifelse(average(system.cpu.system.pct)>0,0,1) + ifelse(average(system.cpu.user.pct)==10,0,1) * ifelse(average(system.cpu.system.pct)<200,0,1) + ifelse(average(system.cpu.user.pct)==2,1,0) > 0, 100, ifelse(average(system.cpu.system.pct)==10, 200, 300))'
+    );
+  });
 
   it('should parse a complex equation with many nested conditions and many aggregations', () => {
     const equation =
diff --git a/x-pack/plugins/observability/public/components/custom_threshold/components/rule_condition_chart/painless_tinymath_parser.ts b/x-pack/plugins/observability/public/components/custom_threshold/components/rule_condition_chart/painless_tinymath_parser.ts
index 0bbcab23948ba..25ec15d3a808b 100644
--- a/x-pack/plugins/observability/public/components/custom_threshold/components/rule_condition_chart/painless_tinymath_parser.ts
+++ b/x-pack/plugins/observability/public/components/custom_threshold/components/rule_condition_chart/painless_tinymath_parser.ts
@@ -75,13 +75,16 @@ export class PainlessTinyMathParser {
   }
 
   replaceCharactersWithAggMap(inputString: string, aggMap: AggMap): string {
-    // Use a regular expression to match any character from 'A' to 'Z'
-    const regex = /[A-Z]/g;
-
-    return inputString.replace(regex, (match) => {
-      const replacement = aggMap[match]; // Get the replacement from the map
-      return replacement ? replacement : match; // Use the replacement or the original character
-    });
+    let parsedInputString = inputString;
+    // Iterate over aggregation names and replace them with equation
+    Object.keys(aggMap)
+      .sort()
+      .reverse()
+      .forEach((metricName) => {
+        parsedInputString = parsedInputString.replaceAll(metricName, aggMap[metricName]);
+      });
+
+    return parsedInputString;
   }
 
   parseCondition(condition: string): string {