cool down vs expand

cool down

verb
  • To become less agitated or excited. 

  • To become cooler; to be reduced in temperature. 

  • 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. 

expand

verb
  • To feel generous or optimistic. 

  • To become, by rewriting, a longer, yet equivalent sum of terms. 

  • To multiply both the numerator and the denominator of a fraction by the same natural number yielding a fraction of equal value 

  • To change (something) from a smaller form or size to a larger one; to spread out or lay open. 

  • To change or grow from smaller to larger in form, number, or size. 

  • To rewrite (an expression) as a longer, yet equivalent sum of terms. 

  • To increase the extent, number, volume or scope of (something). 

  • To express (something) at length and/or in detail. 

  • To increase in extent, number, volume or scope. 

  • To speak or write at length or in detail. 

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