agitate vs tug at someone's heartstrings

agitate

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

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

tug at someone's heartstrings

How often have the words agitate and tug at someone's heartstrings occurred in a corpus of books? (source: Google Ngram Viewer )