half bathroom vs wash room

half bathroom

noun
  • A bathroom with a toilet and (usually) a sink, but no shower or bathtub. 

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. 

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