acerbate vs aggrieve

acerbate

verb
  • To make bitter or sour. 

  • To exasperate; to irritate. 

adj
  • Embittered; having a sour disposition or nature. 

aggrieve

verb
  • To cause someone to feel pain or sorrow to; to afflict 

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