vulva vs weaker sex

vulva

noun
  • The external female sexual organs, collectively. 

  • A protrusion on the side of a nematode. 

weaker sex

noun
  • Women; the female gender. 

  • Used other than figuratively or idiomatically: see weaker, sex. 

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