BOB vs prat

BOB

noun
  • Vibrator (device designed to stimulate a woman's genitals). 

adj
  • Back-of-the-book; denoting those stamps in a catalogue that are not used for the payment of regular postage fees, and are displayed separately in the catalogue after that listing; the division between these two groups varies with the publisher. 

prat

noun
  • The female genitals. 

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

  • A fool. 

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

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