agitate vs fibrillate

agitate

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

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

fibrillate

verb
  • To make rapid irregular movements. 

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