sweet Fanny Adams vs null

sweet Fanny Adams and null both are nouns.

Word	Noun	Adjective	Verb	Adverb
sweet Fanny Adams	Yes	No	No	No
null	Yes	Yes	No	No

As nouns, null is a hypernym of sweet Fanny Adams; that is, null is a word with a broader meaning than sweet Fanny Adams:

sweet Fanny Adams: little or nothing at all
null: a quantity of no importance; thing (object:), singular, negative pronoun; pronoun, thing, singular; quantifier: negative existential

Other hypernyms of sweet Fanny Adams include aught, cipher, cypher, goose egg, nada, naught, nil, nix, nothing, zero, zilch, zip, zippo.

sweet Fanny Adams (noun)	null (noun)
little or nothing at all	a quantity of no importance; thing (object:), singular, negative pronoun; pronoun, thing, singular; quantifier: negative existential

sweet Fanny Adams (adjective)	null (adjective)
	lacking any legal or binding force