cool off vs do a slow burn

cool off

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

  • To decrease in temperature, activity, or temper. 

do a slow burn

verb
  • To experience a gradually increasing feeling of anger or frustration; to slowly burn. 

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