rock the boat vs unnerve

rock the boat

verb
  • To disturb the status quo or go against rules or conventions, as in an effort to get attention. 

  • I'd just jump in and fix it, but that's not my job, and I don't want to rock the boat. 

unnerve

verb
  • To make somebody nervous, upset, alarm, shake the resolve of. 

  • To deprive of nerve, force, or strength; to weaken; to enfeeble. 

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