plunge pool vs pond

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. 

pond

noun
  • An inland body of standing water of any size that is fed by springs rather than by a river. 

  • The Atlantic Ocean. Especially in across the pond. 

  • An inland body of standing water, either natural or man-made, that is smaller than a lake. 

verb
  • To block the flow of water so that it can escape only through evaporation or seepage; to dam. 

  • To make into a pond; to collect, as water, in a pond by damming. 

  • To form a pond; to pool. 

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