flush toilet vs porta-potty

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. 

porta-potty

noun
  • A portable toilet, (in UK, particularly) a chemical toilet comprising only the fixture rather than an entire enclosure. 

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