acerbate vs exacerbate

acerbate

verb
  • To make bitter or sour. 

  • To exasperate; to irritate. 

adj
  • Embittered; having a sour disposition or nature. 

exacerbate

verb
  • To make worse (a problem, bad situation, negative feeling, etc.); aggravate; exasperate. 

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