Other forms: agnomina
An agnomen is an extra descriptor added to someone's name. Having an agnomen may indicate that someone is noteworthy for a significant achievement, or it may be used to distinguish someone from others with similar names.
The practice of using agnomens began in ancient Rome, where an agnomen was a fourth, optional part of a name, usually bestowed in recognition of military or civic achievement. For example, Africanus, meaning "of Africa," was added to the name of Publius Cornelius Scipio after his military victory over Carthage in Northern Africa. Over time, the term agnomen has been loosely applied to any additional descriptive name, also known as an epithet, such as "the Lucky" in "Leif the Lucky," or "the Conqueror" in "William the Conqueror."