Nero Claudius Drusus
As a minimum, a Roman "agnomen" is a name attached to an individual's full titulature after birth and formal naming by the family. True Roman nicknames, fully replacing the individual's name in usage, are rare. One such example where the nickname fully replaced the individual's name in usage was the Emperor Caligula, where that name was used in place of, and not along with, his full name, which was Gaius Julius Caesar Augustus Germanicus. Caligula's "praenomen" was Gaius, his "nomen" Julius, his "cognomen" Caesar. Some "agnomina" were inherited like "cognomen" were, thus establishing a sub-family. Caligula's "agnomen" came from the little boots he wore as part of his miniature soldier's uniform while accompanying his father Germanicus on campaigns in northern Germania. In turn, Germanicus received his agnomen in 9 BC, when it was posthumously awarded to his father Nero Claudius Drusus in honour of his Germanic victories. At birth, Germanicus had been known as either Nero Claudius Drusus after his father or Tiberius Claudius Nero after his uncle. As with Caligula, Germanicus is mostly referred to by his agnomen.