acerbate vs aggravate

acerbate

verb
  • To exasperate; to irritate. 

  • To make bitter or sour. 

adj
  • Embittered; having a sour disposition or nature. 

aggravate

verb
  • To exasperate; to provoke or irritate. 

  • To make (an offence) worse or more severe; to increase in offensiveness or heinousness. 

  • To make worse; to exacerbate. 

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