wash room vs washroom

wash room

noun
  • A bathroom, lavatory, toilet, restroom, or powder room. 

  • An unfurnished room within a building used for hand washing, bathing, laundry, dish washing, etc. 

  • A lavatory; a room designed and equipped for washing hands, normally fitted with basins or sinks, drains, and running water available from taps or faucets. 

  • A similarly equipped room in an institution, such as a hospital or school or manufactory, designated for washing hands, bathing, laundering, or a combination of such. 

  • A specially designed chamber in a laboratory or industrial plant designed for emergency bathing such as may be needed for human exposure to harmful chemicals and the like. 

washroom

noun
  • A room with a toilet, particularly a public toilet. 

  • A room intended to wash the face and hands. 

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