an additional, fourth name given to a person by the ancient Romans in allusion to some achievement or other circumstance, as “Africanus” in “Publius Cornelius Scipio Africanus.” Compare cognomen( def 3 ).
2.
a nickname.
Origin: 1745–55; < Late Latin, equivalent to ad-ad- + nōmen name, with alteration to ag- through influence of agnōscere; see agnize