know vs voucher

know

verb
  • To perceive the truth or factuality of; to be certain of or that. 

  • To experience. 

  • To understand or have a grasp of through experience or study. 

  • To be or become aware or cognizant. 

  • To be able to play or perform (a song or other piece of music). 

  • To be acquainted or familiar with; to have encountered. 

  • To be aware of; to be cognizant of. 

  • To recognize as the same (as someone or something previously encountered) after an absence or change. 

  • To have knowledge; to have information, be informed. 

noun
  • Knowledge; the state of knowing. 

  • Knowledge; the state of knowing; now confined to the fixed phrase ‘in the know’ 

voucher

verb
  • To establish the authenticity of; to vouch for. 

  • To provide (a beneficiary) with a voucher. 

  • To provide a vouch for (an expenditure). 

noun
  • A copy of a published advertisement sent by the agency to the client as proof of publication. 

  • A receipt. 

  • One who or that which vouches. 

  • A mechanical device used in shops for automatically registering the amount of money drawn. 

  • A piece of paper that entitles the holder to a discount, or that can be exchanged for goods and services. 

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