lead in one's pencil vs peter

lead in one's pencil

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

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

peter

noun
  • The penis. 

  • A prison cell. 

  • A safe. 

verb
  • Chiefly followed by out: originally (mining), of a vein of ore: to be depleted of ore; now (generally), to diminish to nothing; to dwindle, to trail off. 

  • Synonym of blue peter 

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