hollo vs yowl

hollo and yowl both are nouns.

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

As nouns, hollo and yowl are synonyms defined as:

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

hollo (noun)	yowl (noun)
a very loud utterance (like the sound of an animal)	a very loud utterance (like the sound of an animal)

hollo (verb)	yowl (verb)
utter a sudden loud cry	utter shrieks, as of cats
cry hollo	cry loudly, as of animals
encourage somebody by crying hollo