lead in one's pencil vs prong

lead in one's pencil

noun
  • A state of erection of one's penis. 

  • Used other than figuratively or idiomatically: see lead, pencil. 

prong

noun
  • The penis. 

  • A thin, pointed, projecting part, as of an antler or a fork or similar tool. A tine. 

  • A branch; a fork. 

verb
  • To pierce or poke with, or as if with, a prong. 

How often have the words lead in one's pencil and prong occurred in a corpus of books? (source: Google Ngram Viewer )