earth closet vs outhouse

earth closet

noun
  • An outhouse or lavatory which uses a cesspit rather than a flush toilet and plumbing. 

outhouse

noun
  • An outbuilding, typically permanent, containing a toilet or seat over a cesspit. 

verb
  • To house in a separate building. 

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