BOB vs diaphragm

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. 

diaphragm

noun
  • A contraceptive device consisting of a flexible cup, used to cover the cervix during intercourse. 

  • In a speaker, the thin, semi-rigid membrane which vibrates to produce sound. 

  • A thin opaque structure with a central aperture, used to limit the passage of light into a camera or similar device. 

  • Any of various membranes or sheets of muscle or ligament which separate one cavity from another. 

  • A floor slab, metal wall panel, roof panel or the like, having a sufficiently large in-plane shear stiffness and sufficient strength to transmit horizontal forces to resisting systems. 

  • A flexible membrane separating two chambers and fixed around its periphery that distends into one or other chamber as the difference in the pressure in the chambers varies. 

  • In mammals, a sheet of muscle separating the thorax from the abdomen, contracted and relaxed in respiration to draw air into and expel air from the lungs; also called thoracic diaphragm. 

  • A permeable or semipermeable membrane. 

verb
  • To reduce lens aperture using an optical diaphragm. 

  • To act as a diaphragm, for example by vibrating. 

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