falsify vs knock down

falsify

verb
  • To counterfeit; to forge. 

  • To misrepresent. 

  • To alter so as to make false; to make incorrect. 

  • To prove to be false. 

  • To show (an item of charge inserted in an account) to be wrong. 

knock down

verb
  • To demolish. 

  • To drink fast. 

  • To disassemble for shipment. 

  • To reduce the price of. 

  • To hit or knock (something or someone), intentionally or accidentally, so that it falls. 

  • To approve a drinking toast by banging glasses on the table. 

  • At an auction, to declare (something) sold with a blow from the gavel. 

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