female genitals vs fanny

female genitals and fanny both are nouns.

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

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

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

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