A cognomen was the third name of a citizen of ancient Rome, under Roman naming conventions. Initially, it was a nickname, but lost that purpose when it became hereditary. Hereditary cognomina were used to augment the second name, the gens, in order to identify a particular branch within a family or family within a clan. The term has also taken on other contemporary meanings.
Because of the limited nature of the Latin praenomen, the cognomen developed to distinguish branches of the family from one another, and occasionally, to highlight an individual's achievement, typically in warfare. One example of this is Gnaeus Pompeius Magnus, whose cognomen Magnus was earned after his military victories under Sulla's dictatorship. The cognomen was a form of distinguishing people who made important feats, and those who already bore a cognomen were awarded another exclusive name, the agnomen. For example, Publius Cornelius Scipio received the agnomen Africanus after his victory over the Carthaginian general Hannibal at Zama, Africa ; and the same procedure occurred in the names of Quintus Caecilius MetellusNumidicus and Quintus Caecilius MetellusMacedonicus. In contrast to the honorary cognomina adopted by successful generals, most cognomina were based on a physical or personality quirk; for example, Rufus meaning "red-haired" or Scaevola meaning "left-handed". Some cognomina were hereditary : others tended to be individual. And some names appear to have been used both as praenomen, agnomen, or non-hereditary cognomen. For instance, Vopiscus was used as both praenomen and cognomen in the Julii Caesares; likewise Nero among the early imperial Claudii, several of whom used the traditional hereditary Claudian cognomen as a praenomen. The upper-class usually used the cognomen to refer to one another. Today, we refer to many prominent ancient Romans by only their cognomen; for example, Cicero serves as a shorthand for Marcus Tullius Cicero, and Caesar for Gaius Julius Caesar.
As a contemporary term
The term "cognomen" has come into use as an English noun used outside the context of Ancient Rome. According to the 2012 edition of the Random House Dictionary, cognomen can mean a "surname" or "any name, especially a nickname". The basic sense in English is "how one is well known". For example Alfred the Great. Catalan cognom and Italiancognome, derived from the Latin cognomen, mean "family name". Maltese kunjom is derived from the Italian version, retaining the same meaning. The term "cognomen" can also be applied to cultures with a clan structure and naming conventions comparable to those of Ancient Rome; thus, hereditary "cognomina" have been described as in use among the Xhosa, the Igbo, the Yoruba, or the Zulu.
