bellyache vs gripe

bellyache and gripe both are nouns.

Word	Noun	Adjective	Verb	Adverb
bellyache	Yes	No	Yes	No
gripe	Yes	No	Yes	No

As verbs, bellyache and gripe are synonyms defined as:

Other synonyms of bellyache include beef, bitch, crab, grouse, holler, squawk.

bellyache (noun)	gripe (noun)
an ache localized in the stomach or abdominal region	informal terms for objecting

bellyache (verb)	gripe (verb)
complain	complain