BOB vs copulation

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. 

copulation

noun
  • Sexual procreation between a man and a woman or transfer of the sperm from male to female; usually applied to the mating process in nonhuman animals; coitus; coition. 

  • The act of coupling or joining; union; conjunction. 

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