knickknackery vs rarity

knickknackery and rarity both are nouns.

Word	Noun	Adjective	Verb	Adverb
knickknackery	Yes	No	No	No
rarity	Yes	No	No	No

As nouns, rarity is a hypernym of knickknackery; that is, rarity is a word with a broader meaning than knickknackery:

Other hypernyms of knickknackery include curio, curiosity, oddity, oddment, peculiarity.

knickknackery (noun)	rarity (noun)
miscellaneous curios	something unusual -- perhaps worthy of collecting
	a rarified quality
	noteworthy scarcity