knickknack vs oddity

knickknack and oddity both are nouns.

Word	Noun	Adjective	Verb	Adverb
knickknack	Yes	No	No	No
oddity	Yes	No	No	No

As nouns, oddity is a hypernym of knickknack; that is, oddity is a word with a broader meaning than knickknack:

Other hypernyms of knickknack include curio, curiosity, oddment, peculiarity, rarity.

knickknack (noun)	oddity (noun)
miscellaneous curios	something unusual -- perhaps worthy of collecting
a small inexpensive mass-produced article	a strange attitude or habit
	eccentricity that is not easily explained