agitate vs light a fire under

agitate

verb
  • To disturb or excite; to perturb or stir up (a person). 

  • To cause to move with a violent, irregular action; to shake. 

light a fire under

verb
  • To motivate or encourage (someone) to start sooner or move faster. 

How often have the words agitate and light a fire under occurred in a corpus of books? (source: Google Ngram Viewer )