knock off vs undress

knock off

verb
  • To remove by hitting (something, someone) 

  • To rob. 

  • To defeat. 

  • 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 kill. 

  • To accomplish hastily. 

undress

verb
  • To strip of something. 

  • To remove the clothing of (someone). 

  • To remove one's clothing. 

  • To remove one’s clothing. 

  • To take the dressing, or covering, from. 

noun
  • Partial or informal dress for women, as worn in the home rather than in public. 

  • Informal clothing for men, as opposed to formal or ceremonial wear. 

  • Now more specifically, a state of having few or no clothes on. 

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