moniker vs cognomen

moniker and cognomen both are nouns.

Word	Noun	Adjective	Verb	Adverb
moniker	Yes	No	No	No
cognomen	Yes	No	No	No

As nouns, moniker and cognomen are synonyms defined as:

moniker and cognomen: a familiar name for a person (often a shortened version of a person's given name)

Other synonyms of moniker include byname, nickname, sobriquet, soubriquet.

moniker (noun)	cognomen (noun)
a familiar name for a person (often a shortened version of a person's given name)	the name used to identify the members of a family (as distinguished from each member's given name)
	a familiar name for a person (often a shortened version of a person's given name)