extinguish vs keep it down

extinguish

verb
  • To obscure or eclipse something. 

  • To hunt down (a species) to extinction. 

  • To bring about the extinction of a conditioned reflex. 

  • To put out, as in fire; to end burning; to quench. 

  • To destroy or abolish something. 

  • To die out. 

  • To kill. 

keep it down

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