knap vs twirl

knap

verb
  • To make a sound of snapping. 

  • To rap or strike sharply. 

  • To shape a brittle material having conchoidal fracture, usually a mineral (flint, obsidian, chert etc.), by breaking away flakes, often forming a sharp edge or point. 

noun
  • A protuberance; a swelling; a knob. 

  • A small hill 

  • A sharp blow or slap. 

  • The crest of a hill 

twirl

verb
  • To perform a twirl. 

  • To twist round. 

  • To pitch. 

  • To rotate rapidly. 

noun
  • A little twist of some substance; a swirl. 

  • A movement where a person spins round elegantly; a pirouette. 

  • Any rotating movement; a spin. 

  • A prison guard. 

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