grumbler vs bellyacher

grumbler and bellyacher both are nouns.

Word	Noun	Adjective	Verb	Adverb
grumbler	Yes	No	No	No
bellyacher	Yes	No	No	No

As nouns, grumbler and bellyacher are synonyms defined as:

grumbler and bellyacher: a person given to excessive complaints and crying and whining

Other synonyms of grumbler include complainer, crybaby, moaner, sniveller, squawker, whiner.

grumbler (noun)	bellyacher (noun)
a person given to excessive complaints and crying and whining	a person given to excessive complaints and crying and whining