cognomen

nouns

a familiar name for a person (often a shortened version of a person's given name)
"Joe's mother would not use his nickname and always called him Joseph"; "Henry's nickname was Slim"
byname, cognomen, moniker, nickname, sobriquet, soubriquet
the name used to identify the members of a family (as distinguished from each member's given name)
cognomen, family name, last name, surname