nub vs sugar plum

nub

verb
  • To push; to nudge. 

  • To beckon. 

  • To hit the ball weakly. 

noun
  • a pointing stick 

  • The clitoris. 

  • A small lump or knob. 

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

sugar plum

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