ignite vs stir up

ignite

verb
  • to spark off (something), to trigger 

  • to commence burning. 

  • to set fire to (something), to light (something) 

  • To subject to the action of intense heat; to heat strongly; often said of incombustible or infusible substances. 

stir up

verb
  • To arouse or excite (passion or action). 

  • To move or disturb slightly; to make turbid. 

  • To mix (ingredients) by stirring. 

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