baths vs plunge pool

baths

noun
  • A building containing a public swimming pool or shower facilities; originally a place having individual cubicles where people without bathrooms could have a bath. 

plunge pool

noun
  • A pool that is small in diameter, but deep, usually resulting from erosion by a natural force such as a waterfall or rapids. 

How often have the words baths and plunge pool occurred in a corpus of books? (source: Google Ngram Viewer )