chummy vs chum

chummy is not a noun while chum is a noun.

Word	Noun	Adjective	Verb	Adverb
chummy	No	Yes	No	No
chum	Yes	No	No	No

chummy (noun)	chum (noun)
	a large Pacific salmon with small spots on its back; an important food fish
	bait consisting of chopped fish and fish oils that are dumped overboard to attract fish
	a close friend who accompanies his buddies in their activities

chummy (adjective)	chum (adjective)
(used informally) associated on close terms
(used colloquially) having the relationship of friends or pals