quiet down vs spin down

quiet down

verb
  • To diminish in intensity. 

  • To make someone or something become quieter. 

  • To become quieter. 

spin down

verb
  • To diminish in energy; to slow down or peter out; to be gradually canceled or ended. 

  • To reduce its speed of rotation. 

  • To reduce its spinning speed from that required for reading and writing. 

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