disturb vs unsettle

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. 

unsettle

verb
  • To make upset or uncomfortable 

  • To bring into disorder or disarray 

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