fan the flames vs hit on

fan the flames

verb
  • To intensify or worsen an already difficult situation. 

hit on

verb
  • To discover, pinpoint; to think up; to realize. 

  • To flirt with; to approach and speak to (someone), seeking romance, love, sex, etc. 

How often have the words fan the flames and hit on occurred in a corpus of books? (source: Google Ngram Viewer )