cool down vs foster

cool down

verb
  • 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 decrease in degree or intensity. 

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

foster

verb
  • To cultivate and grow something. 

  • To nurture or bring up offspring, or to provide similar parental care to an unrelated child. 

  • To nurse or cherish something. 

noun
  • A foster parent. 

  • The care given to another; guardianship. 

adj
  • Related by such care. 

  • Receiving such care. 

  • Providing parental care to children not related to oneself. 

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