byname vs appellation

byname and appellation both are nouns.

Word	Noun	Adjective	Verb	Adverb
byname	Yes	No	No	No
appellation	Yes	No	No	No

As nouns, appellation is a hypernym of byname; that is, appellation is a word with a broader meaning than byname:

byname: a familiar name for a person (often a shortened version of a person's given name)
appellation: identifying word or words by which someone or something is called and classified or distinguished from others

Other hypernyms of byname include appellative, denomination, designation.

byname (noun)	appellation (noun)
a familiar name for a person (often a shortened version of a person's given name)	identifying word or words by which someone or something is called and classified or distinguished from others
	a geographical indication used to identify where the grapes for a wine are grown