dement vs perturb

dement

verb
  • To drive mad; to craze 

noun
  • An insane person, or one afflicted with dementia 

perturb

verb
  • To disturb; to bother or unsettle. 

  • To modify the motion of a body by exerting a gravitational force. 

  • To modify slightly, such as an equation or value. 

  • To slightly modify the motion of an object. 

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