promisor vs vower

promisor and vower both are nouns.

Word	Noun	Adjective	Verb	Adverb
promisor	Yes	No	No	No
vower	Yes	No	No	No

As nouns, vower is a hyponym of promisor; that is, vower is a word with a more specific, narrower meaning than promisor:

promisor: a person who makes a promise
vower: someone who makes a solemn promise to do something or behave in a certain way

promisor (noun)	vower (noun)
a person who makes a promise	someone who makes a solemn promise to do something or behave in a certain way