novelty vs knickknack

novelty and knickknack both are nouns.

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

As nouns, novelty and knickknack are synonyms defined as:

novelty (noun)	knickknack (noun)
cheap showy jewelry or ornament on clothing	miscellaneous curios
a small inexpensive mass-produced article	a small inexpensive mass-produced article
originality by virtue of being refreshingly novel
originality by virtue of being new and surprising