BOB vs jade stalk

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. 

jade stalk

noun
  • The penis, especially in reference to sex. 

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