heartburn vs stomachache

heartburn

noun
  • A burning pain in the chest that is caused by stomach acid entering the gullet. 

stomachache

noun
  • A pain in the abdomen, often caused by indigestion. (The pain is usually lower than the stomach and related to the intestines.) 

How often have the words heartburn and stomachache occurred in a corpus of books? (source: Google Ngram Viewer )