spark off vs stir up

spark off

verb
  • To initiate something by providing the necessary conditions. 

stir up

verb
  • To move or disturb slightly; to make turbid. 

  • To arouse or excite (passion or action). 

  • To mix (ingredients) by stirring. 

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