Agnomen

1. n. An additional name, or an epithet appended to a name; as, Aristides the Just.
2. n. An additional or fourth name given by the Romans, on account of some remarkable exploit or event; as, Publius Caius Scipio Africanus.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.