acerbate vs exasperate

acerbate

verb
  • To exasperate; to irritate. 

  • To make bitter or sour. 

adj
  • Embittered; having a sour disposition or nature. 

exasperate

verb
  • To tax the patience of; irk, frustrate, vex, provoke, annoy; to make angry. 

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