Noun
A surname.
The last of the three names of a person among the ancient Romans, denoting his house or family.
Source: Webster's dictionaryJoe's mother would not use his nickname and always called him Joseph Source: Internet
Henry's nickname was Slim Source: Internet
But as Roman institutions vanished, and the distinction between nomen and cognomen ceased to have any practical importance, so the complex system of cognomina that developed under the later empire faded away. Source: Internet
Decline and fall Otho He accepted, or appeared to accept, the cognomen of Nero conferred upon him by the shouts of the populace, whom his comparative youth and the effeminacy of his appearance reminded of their lost favourite. Source: Internet
Depending on whether Pliny meant that Agrippa was aged 50 or 51 at his death, this gives a date of birth between March 64 and March 62. His family cognomen was the Latin form of Greek Agrippas, meaning "wild horse". Source: Internet
Both inscriptions are from Roman Spain, and are also notable for the doubled nomen and for the cognomen Secunda, which in this case is really a praenomen placed after the filiation, a common practice in Roman women's names of this period. Source: Internet