acerbate vs groan

acerbate

verb
  • To make bitter or sour. 

  • To exasperate; to irritate. 

adj
  • Embittered; having a sour disposition or nature. 

groan

verb
  • To make a groan. 

  • To seemingly creak under the strain of being heavily laden. 

noun
  • A low, mournful sound uttered in pain or grief. 

  • A low, guttural sound uttered in frustration, disapproval, or ecstasy. 

  • A low creaking sound from applied pressure or weight. 

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