pull back vs tremble

pull back

verb
  • Used other than figuratively or idiomatically: see pull, back. 

  • To retreat. 

  • To pass (the ball) into a position further from the attacking goal line. 

  • To score when the team is losing. 

tremble

verb
  • To shake, quiver, or vibrate. 

  • To fear; to be afraid. 

noun
  • A shake, quiver, or vibration. 

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