crapper vs necessarium

crapper

noun
  • A lavatory or outhouse. 

  • A rapper, or a performer of rap music. 

  • A chamber pot or toilet, particularly (dated) a flush toilet by Thomas Crapper. 

  • A half-glass of whiskey. 

necessarium

noun
  • A lavatory. 

  • Synonym of reredorter: a monastery's latrine, outhouse, or lavatory, typically located behind the dormitory. 

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