fan the flames vs foment

fan the flames

verb
  • To intensify or worsen an already difficult situation. 

foment

verb
  • To incite or cause troublesome acts; to encourage; to instigate. 

  • To apply a poultice to; to bathe with a cloth or sponge. 

noun
  • Fomentation. 

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