hollo vs let loose

hollo is a noun but let loose is not a noun.

Word	Noun	Adjective	Verb	Adverb
hollo	Yes	No	Yes	No
let loose	No	No	Yes	No

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

Other hypernyms of hollo include emit, let out, utter.

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

hollo (verb)	let loose (verb)
utter a sudden loud cry	express audibly; utter sounds (not necessarily words)
cry hollo	turn loose or free from restraint
encourage somebody by crying hollo