knock vs knocking

knock

noun
  • Preignition, a type of abnormal combustion occurring in spark ignition engines caused by self-ignition; also, the characteristic knocking sound associated with it. 

  • An abrupt rapping sound, as from an impact of a hard object against wood. 

  • A sharp impact. 

  • A batsman's innings. 

  • A blow or setback. 

  • Synonym of hunger knock 

  • A criticism. 

verb
  • To criticize verbally; to denigrate; to undervalue. 

  • To kick a ball towards another player; to pass. 

  • To rap one's knuckles against something, especially wood. 

knocking

noun
  • A repetitive ping, knock, or similar sound coming from an engine in which there are repeated uncontrolled explosions in the combustion chamber. 

  • An act in which something is knocked on, or the sound thus produced 

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