destroy vs knock off

destroy

verb
  • To defeat soundly. 

  • To sing a song poorly. 

  • To put down or euthanize. 

  • To remove data. 

  • To exhaust duly and thus recreate or build up. 

  • To penetrate sexually in an aggressive way. 

  • To damage beyond use or repair. 

  • To severely disrupt the well-being of (a person); ruin. 

  • To neutralize, undo a property or condition. 

knock off

verb
  • To defeat. 

  • To rob. 

  • To halt one's work or other activity. 

  • To have sex with. 

  • To remove, as a discount or estimate. 

  • To make a copy of, as of a design. 

  • To assign (an item) to a bidder at an auction, indicated by knocking on the counter. 

  • To remove by hitting (something, someone) 

  • To kill. 

  • To accomplish hastily. 

How often have the words destroy and knock off occurred in a corpus of books? (source: Google Ngram Viewer )