acerbate vs madden

acerbate

verb
  • To make bitter or sour. 

  • To exasperate; to irritate. 

adj
  • Embittered; having a sour disposition or nature. 

madden

verb
  • To make angry. 

  • To make insane; to inflame with passion. 

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