cognomen

A cognomen is a personal name that accompanies a given name to identify a person within a larger family or clan. The term comes from Latin cognomen, derived from com- “with” and nomen “name,” conveying an “additional” or nickname name that may be acquired during life or inherited.

In ancient Rome, the full name typically had three parts: praenomen (given name) chosen by family, nomen (gens name) identifying the clan, and cognomen (the branch or distinguishing nickname). The cognomen could reflect a trait, origin, achievement, or designate a hereditary branch; over time many cognomina became hereditary and functioned as a surname within a gens. Notable examples include Julius Caesar (Caesar as his cognomen) and Marcus Tullius Cicero (Cicero as his cognomen).

Today, cognomen is mainly a term in scholarly discussions of ancient onomastics and Roman history; in modern contexts, cognomen is often treated as synonymous with surname or family name, though its origin as a separate third name reflects a different naming system. The cognomen concept illustrates how personal naming can encode kinship, status, and lineage.