acerbate vs curdle

acerbate

verb
  • To make bitter or sour. 

  • To exasperate; to irritate. 

adj
  • Embittered; having a sour disposition or nature. 

curdle

verb
  • To clot or coagulate; to cause to congeal, such as through cold. (metaphorically of blood) 

  • To form curds so that it no longer flows smoothly; to cause to form such curds. (usually said of milk) 

  • To cause a liquid to spoil and form clumps so that it no longer flows smoothly 

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