hollo vs holler

hollo and holler both are nouns.

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

As nouns, hollo and holler are synonyms defined as:

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

As verbs, hollo and holler are synonyms defined as:

Other synonyms of hollo include call, cry, scream, shout, shout out, squall, yell.

As verbs, holler is a hypernym of hollo; that is, holler is a word with a broader meaning than hollo:

Other hypernyms of hollo include call, cry, hollo, scream, shout, shout out, squall, yell.

hollo (noun)	holler (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

hollo (verb)	holler (verb)
utter a sudden loud cry	complain
cry hollo	utter a sudden loud cry
encourage somebody by crying hollo	shout out