cool off vs flare up

cool off

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

  • To decrease in temperature, activity, or temper. 

flare up

verb
  • To become more intense suddenly. 

  • To burst out suddenly, as in anger. 

  • To burn brightly again. 

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