Cognomen

A cognomen (/kɒɡˈnoʊmən/, Latin: [koːŋˈnoːmen]; Latin plural cōgnōmina; con- "together with" and (g)nōmen "name") was the third name of a citizen of ancient Rome, under Roman naming conventions. Initially, it was a nickname, but it lost that purpose when it became hereditary. Hereditary cognomina were used to augment the second name (the family name, or clan name) in order to identify a particular branch within a family or family within a clan. The term has also taken on other contemporary meanings.