carob bean tree vs carob bean

carob bean tree and carob bean both are nouns.

Word	Noun	Adjective	Verb	Adverb
carob bean tree	Yes	No	No	No
carob bean	Yes	No	No	No

carob bean tree (noun)	carob bean (noun)
evergreen Mediterranean tree with edible pods; the biblical carob	long pod containing small beans and sweetish edible pulp; used as animal feed and source of a chocolate substitute