fanny vs genital organ

fanny and genital organ both are nouns.

Word	Noun	Adjective	Verb	Adverb
fanny	Yes	No	No	No
genital organ	Yes	No	No	No

As nouns, genital organ is a hypernym of fanny; that is, genital organ is a word with a broader meaning than fanny:

Other hypernyms of fanny include crotch, genitalia, genitals, private parts, privates.

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