john vs litter box

john

noun
  • A device or place to urinate and defecate: now usually a toilet or lavatory, but also (dated) a chamber pot or outhouse. 

  • A male mule. 

  • A Western man traveling in East Asia. 

  • A prostitute's client. 

litter box

noun
  • A box used to provide a soiling area for (usually) pet cats, generally filled with kitty litter, sand, clay chips, etc. 

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