cool off vs let go

cool off

verb
  • To decrease in temperature, activity, or temper. 

  • To cause to decrease in temperature, activity or temper. 

let go

verb
  • To emotionally disengage or to distract oneself from a situation. 

  • To dismiss from employment. 

  • To release from one's grasp; to go from a state of holding on to a state of no longer holding on. 

  • To ignore (a comment, etc.). 

  • To fail to maintain a standard of appearance, behavior, or performance. 

  • Used other than figuratively or idiomatically: see let, go. 

  • To gain weight 

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