knob vs tubercle

knob

noun
  • A rounded protuberance, especially one arising from a flat surface; a fleshy lump or caruncle. 

  • A ball-shaped part of a handle, lever, etc., designed to be grabbed by the hand. 

  • The head of the penis; the glans. 

  • A woman's breast. 

  • A contemptible person; dick. 

  • A prominent rounded hill. 

  • A freshman at The Citadel, The Military College of South Carolina. 

  • The clitoris. 

  • A rounded control switch that can be turned on its axis, designed to be operated by the fingers. 

  • A prominent, rounded bump along a mountain ridge. 

  • A dollop, an amount just larger than a spoonful (usually referring to butter). 

  • A chunky branch-like piece, especially of a ginger rhizome. 

  • A bulb of the garlic plant consisting of multiple cloves. 

  • A rounded ornament on the hilt of an edged weapon; a pommel. 

verb
  • To have sex with. 

tubercle

noun
  • A small rounded nodule forming the characteristic lesion of tuberculosis. 

  • A round nodule, small eminence, or warty outgrowth, especially those found on bones for the attachment of a muscle or ligament or small elevations on the surface of a tooth. 

  • A small rounded wartlike protuberance of the roots of some leguminous plants; the lip of certain orchids, cacti. 

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