IPA: /æɡˈnoʊmən/
KK: /æɡˈnoʊmən/
A special name added to a person's name in ancient Rome, usually to honor them for achievements or victories.
Julius Caesar was often referred to by his agnomen, which celebrated his achievements.
Agnomen → It is formed from "ad-" (meaning to) and "nomen" (meaning name). The term originally referred to an additional name given to a person, often to signify a particular characteristic or achievement, thus meaning an added name.
Think of 'adding' something ('ad-') to a 'name' ('nomen') — that's why agnomen means an additional name.