knickknack vs nicknack

knickknack and nicknack both are nouns.

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

As nouns, knickknack and nicknack are synonyms defined as:

Other synonyms of knickknack include bric-a-brac, knickknackery, whatnot.

knickknack (noun)	nicknack (noun)
miscellaneous curios	miscellaneous curios
a small inexpensive mass-produced article