[2] Because the great majority of Roman gentilicia end in -ius, many writers have supposed Norbanus to have been a cognomen, perhaps belonging to a branch of the Junia gens.
In fact, it is itself a nomen gentilicium, belonging to a class of nomina derived from place-names, and ending in -anus.
[2][3][4] Such names were common in families of Umbrian origin, although less characteristic of Latin gentes.
[5] In the case of the Norbani, the name is likely derived from the town of Norba, in Latium, but, since none of the known members of the gens show any association with the town, it was perhaps an earlier, unknown ancestor who came from there, suggesting the family is of greater antiquity than the available records suggest.
[6][7] For the first Norbani appearing in the late Republic, Ronald Syme suggested an Etruscan origin.