nub vs tubercle

nub

noun
  • A small lump or knob. 

  • a pointing stick 

  • The clitoris. 

  • The essence or core of an issue, argument etc. 

verb
  • To push; to nudge. 

  • To beckon. 

  • To hit the ball weakly. 

tubercle

noun
  • 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 nodule forming the characteristic lesion of tuberculosis. 

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

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