chamber pot vs john

chamber pot

noun
  • A container used for urination and defecation, particularly those used in early modern towns before the advent of the flush toilet. 

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. 

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