flush toilet vs water closet

flush toilet

noun
  • A toilet that uses water to flush urine and feces through a pipe to another location, typically a sewer main in urban settings or a septic tank elsewhere. 

water closet

noun
  • A flush toilet itself. 

  • Used other than figuratively or idiomatically: see water, closet. 

  • A room containing a flush toilet. 

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