lido vs plunge pool

lido

noun
  • An outdoor swimming pool. 

  • Part of the sea by a beach sectioned off for swimming and other aquatic activities. 

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 lido and plunge pool occurred in a corpus of books? (source: Google Ngram Viewer )