acerbate vs vex

acerbate

verb
  • To exasperate; to irritate. 

  • To make bitter or sour. 

adj
  • Embittered; having a sour disposition or nature. 

vex

verb
  • To annoy, irritate. 

  • To toss back and forth; to agitate; to disquiet. 

  • To twist, to weave. 

  • To cause (mental) suffering to; to distress. 

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