sweet young thing vs water nymph

sweet young thing

noun
  • An attractive young woman. 

  • A sweet young woman. 

water nymph

noun
  • A female spirit presiding over fountains, wells, streams, etc. 

  • Any of various aquatic plants of the genus Najas. 

How often have the words sweet young thing and water nymph occurred in a corpus of books? (source: Google Ngram Viewer )