acerbate vs disturb

acerbate

verb
  • To make bitter or sour. 

  • To exasperate; to irritate. 

adj
  • Embittered; having a sour disposition or nature. 

disturb

verb
  • to have a negative emotional impact; to cause emotional distress or confusion. 

  • to divert, redirect, or alter by disturbing. 

  • to confuse a quiet, constant state or a calm, continuous flow, in particular: thoughts, actions or liquids. 

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