sylph vs water nymph

sylph

noun
  • A slender woman or girl, usually graceful and sometimes with the implication of sublime station over everyday people. 

  • The elemental being of air, usually female. 

  • An invisible being of the air. 

  • Any of the mainly dark green and blue hummingbirds (genus Aglaiocercus), the male of which has a long forked tail. 

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 sylph and water nymph occurred in a corpus of books? (source: Google Ngram Viewer )