What is Agnomen?

Legal Definition
Lat. An additional name or title; a nickname. A name or title which a man gets by some action or peculiarity; the last of the four names sometimes given a Roman. Thus, Scipio Africanus, (the African,) from hla African victories. Ainsworth; Calvin.'
-- Black's Law Dictionary
Legal Definition
A popular appellation often appended to one’s true name. Agrarian. Pertaining to land.
-- Ballentine's Law Dictionary