affirmer vs asseverator

affirmer and asseverator both are nouns.

Word	Noun	Adjective	Verb	Adverb
affirmer	Yes	No	No	No
asseverator	Yes	No	No	No

As nouns, affirmer and asseverator are synonyms defined as:

Other synonyms of affirmer include asserter, avower, declarer.

affirmer (noun)	asseverator (noun)
someone who claims to speak the truth	someone who claims to speak the truth