holler vs bellow

holler and bellow both are nouns.

Word	Noun	Adjective	Verb	Adverb
holler	Yes	No	Yes	No
bellow	Yes	No	Yes	No

As nouns, holler and bellow are synonyms defined as:

Other synonyms of holler include bellowing, holla, hollering, hollo, holloa, roar, roaring, yowl.

holler (noun)	bellow (noun)
a very loud utterance (like the sound of an animal)	a very loud utterance (like the sound of an animal)
a small valley between mountains

holler (verb)	bellow (verb)
complain	shout loudly and without restraint
utter a sudden loud cry	make a loud noise, as of animal
shout out