constrain vs cool down

constrain

verb
  • To reduce a result in response to limited resources. 

  • To force physically, by strong persuasion or pressuring; to compel; to oblige. 

  • To keep within close bounds; to confine. 

cool down

verb
  • To decrease in degree or intensity. 

  • To become cooler; to be reduced in temperature. 

  • To become less agitated or excited. 

  • To cause (something) to become cooler; to reduce the temperature of. 

  • To cause (someone) to become less agitated or excited. 

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