acerbate vs frost

acerbate

verb
  • To make bitter or sour. 

  • To exasperate; to irritate. 

adj
  • Embittered; having a sour disposition or nature. 

frost

verb
  • To anger or annoy. 

  • To cover with frost. 

  • To become covered with frost. 

  • To bleach individual strands of hair while leaving adjacent strands untouched. 

  • To sharpen (the points of a horse's shoe) to prevent it from slipping on ice. 

  • To coat (something, e.g. a cake) with icing to resemble frost. 

noun
  • A cover of minute ice crystals on objects that are exposed to the air. Frost is formed by the same process as dew, except that the temperature of the frosted object is below freezing. 

  • Coldness or insensibility; severity or rigidity of character. 

  • The cold weather that causes these ice crystals to form. 

  • A shade of white, like that of frost. 

  • A kind of light diffuser. 

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