prat vs rear end

prat

noun
  • A buttock, or the buttocks; a person's bottom. 

  • A cunning or mischievous trick; a prank, a joke. 

  • The female genitals. 

  • A fool. 

rear end

noun
  • The buttocks. 

  • The back or hindmost part of anything, such as a car. 

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