litter box vs washroom

litter box

noun
  • A box used to provide a soiling area for (usually) pet cats, generally filled with kitty litter, sand, clay chips, etc. 

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 litter box and washroom occurred in a corpus of books? (source: Google Ngram Viewer )