perturb vs scare off

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. 

scare off

verb
  • To cause (something) to flee by frightening it. 

  • To deter 

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