acerbate vs umbrage

acerbate

verb
  • To exasperate; to irritate. 

  • To make bitter or sour. 

adj
  • Embittered; having a sour disposition or nature. 

umbrage

verb
  • To displease or cause offense. 

  • To shade. 

noun
  • A feeling of doubt. 

  • Leaves that provide shade, as the foliage of trees. 

  • A feeling of anger or annoyance caused by something offensive. 

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