agitate vs churn up

agitate

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

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

churn up

verb
  • To make the ground uneven, generally unintentionally. 

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