female genitalia vs fanny

female genitalia and fanny both are nouns.

Word	Noun	Adjective	Verb	Adverb
female genitalia	Yes	No	No	No
fanny	Yes	No	No	No

As nouns, female genitalia and fanny are synonyms defined as:

Other synonyms of female genitalia include female genital organ, female genitals.

female genitalia (noun)	fanny (noun)
external female sex organs	the fleshy part of the human body that you sit on
	external female sex organs