let out vs let go of

let out and let go of both are verbs.

Word	Noun	Adjective	Verb	Adverb
let out	No	No	Yes	No
let go of	No	No	Yes	No

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

Other hypernyms of let out include let go, release, relinquish.

let out (verb)	let go of (verb)
make (clothes) larger	release, as from one's grip
make known to the public information that was previously known only to a few people or that was meant to be kept a secret
express audibly; utter sounds (not necessarily words)
bring out of a specific state