bivalve vs vulva

bivalve

noun
  • A pericarp in which the seed case opens or splits into two parts or valves. 

  • Any mollusc belonging to the taxonomic class Bivalvia, characterized by a shell consisting of two hinged sections, such as a scallop, clam, mussel or oyster. 

vulva

noun
  • A protrusion on the side of a nematode. 

  • The external female sexual organs, collectively. 

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