acerbate vs steam up

acerbate

verb
  • To make bitter or sour. 

  • To exasperate; to irritate. 

adj
  • Embittered; having a sour disposition or nature. 

steam up

verb
  • To become steamy. 

  • To become coated with condensation. To fog up. 

  • To bring (a steam boiler) up to working steam pressure. 

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