knocker vs rapper

knocker

noun
  • A person who knocks (denigrates) something. 

  • A person who knocks. 

  • A critic; one who disparages. 

  • One who defaults on payment of a wager. 

  • A woman's breast. 

  • A large cockroach, especially Blaberus giganteus, of semitropical America, which is able to produce a loud knocking sound. 

  • A large, boulder-shaped outcrop of bedrock in an otherwise low-lying landscape, chiefly associated with a mélange. 

  • A device, usually hinged with a striking plate, used for knocking on a door. 

  • A mechanical device in a pinball table that produces a loud percussive noise. 

rapper

noun
  • The knocker of a door. 

  • A swinging knocker for making signals at the mouth of a shaft. 

  • A flexible strip of metal, 45-60cm long, with handles at each end, used for Northumbrian rapper sword dancing. 

  • A spiritualistic medium who claims to receive communications from spirits in the form of knocking sounds. 

  • A performer of rap music, or someone who raps in any form of music. 

  • A mechanical, or later electric, signalling device formerly used in the mines of north-eastern England to signal to the engineman that the cages carrying men or coals up and down the shaft were ready to be raised or lowered. 

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