cool off vs die away

cool off

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

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

die away

verb
  • To diminish or wane; to cease gradually. 

  • To die gradually or slowly. 

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