affiant vs doer

affiant and doer both are nouns.

Word	Noun	Adjective	Verb	Adverb
affiant	Yes	No	No	No
doer	Yes	No	No	No

As nouns, doer is a hypernym of affiant; that is, doer is a word with a broader meaning than affiant:

Other hypernyms of affiant include actor, worker.

affiant (noun)	doer (noun)
a person who makes an affidavit	a person who acts and gets things done