boff vs knuckle sandwich

boff

noun
  • A hit or smack. 

  • A great success; a hit. 

  • A pupil who works hard; a swot. 

  • A line in a film etc that elicits such a laugh. 

  • A big laugh. 

verb
  • to have sexual intercourse (with someone) 

  • To hit; to strike. 

knuckle sandwich

noun
  • A punch to the face, especially to the mouth. 

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