naiad vs river god

naiad

noun
  • A female deity (nymph) associated with water, especially a spring, stream, or other fresh water. 

  • The aquatic larva (nymph) of a dragonfly or damselfly. 

  • Any of various aquatic plants of the genus Najas. 

river god

noun
  • The tutelary deity of a river. 

How often have the words naiad and river god occurred in a corpus of books? (source: Google Ngram Viewer )