verify vs verifier

verify is not a noun while verifier is a noun.

Word	Noun	Adjective	Verb	Adverb
verify	No	No	Yes	No
verifier	Yes	No	No	No

verify (noun)	verifier (noun)
	someone who vouches for another or for the correctness of a statement

verify (verb)	verifier (verb)
confirm the truth of
to declare or affirm solemnly and formally as true
attach or append a legal verification to (a pleading or petition)
check or regulate (a scientific experiment) by conducting a parallel experiment or comparing with another standard