acerbate vs vitriolic

acerbate

adj
  • Embittered; having a sour disposition or nature. 

verb
  • To exasperate; to irritate. 

  • To make bitter or sour. 

vitriolic

adj
  • Bitterly scathing, caustic. 

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