flipper vs knock out

flipper

verb
  • To lift one or both flippers out of the water and slap the surface of the water. 

noun
  • Television remote control, clicker. 

  • A type of ball bowled by a leg spin bowler, which spins backwards and skids off the pitch with a low bounce. 

  • A flat lever in a pinball machine, triggered by the player to strike the ball and keep it in play. 

  • A kind of false tooth, usually temporary. 

  • A small flat used to support a larger one. 

  • Someone who flips, in the sense of buying a house or other asset and selling it quickly for profit. 

  • Someone who flips in any other sense, for example throwing a coin. 

  • In marine mammals such as whales, a wide flat limb, adapted for swimming. 

  • A flat, wide, paddle-like rubber covering for the foot, used in swimming. 

  • A kitchen spatula. 

knock out

verb
  • To strike or bump (someone or something) out. 

  • To fall asleep, especially suddenly. 

  • To lose the scent of hounds in fox-hunting. 

  • To eliminate from a contest or similar. 

  • To put to sleep. 

  • To complete, especially in haste; knock off. 

  • To render unconscious, as by a blow to the head. 

  • To exhaust. 

  • To cause a mechanism to become non-functional by damaging or destroying it. 

  • To communicate (a message) by knocking. 

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