cognomens

Cognomen is a term used in onomastics to describe an additional name associated with a person, often functioning as a surname or nickname. Etymology: from Latin cognomen, literally “the name that is known together with the nomen,” derived from co- (together) and nomen (name). In the Roman naming system, a male citizen typically bore three names: praenomen (given name), nomen (gens name), and cognomen (family name within the gens). The cognomen often began as a nickname reflecting an attribute, achievement, place of origin, or notable deed, and could become hereditary, forming a stable family surname.

In other contexts, cognomen may simply mean a byname or epithet used to distinguish an individual who shared a given name, and it is sometimes used in scholarly discussions about historical figures. In modern usage, the term is mostly encountered in historical or linguistic works; in ordinary speech, cognomen is generally synonymous with surname or might refer to an informal nickname.

Notable examples from antiquity include Caesar (Gaius Julius Caesar) and Africanus (Scipio Africanus), where the cognomen names a branch of a gens or an achievement. The form became influential outside Rome: the word cognomen is the source of terms that indicate known epithets or bynames, and the practice influenced naming conventions in later European cultures.