The authors agree that this surname has as its base the name Néro, arisen from a nickname linked to the adjective néro ("black"), attributed in reference to the very dark colour of the skin, the hair or the beard, or else in figurative senses of the term. E. De Felice and A. Bongioanni further note that this surname shares its origin with Ranieri, since both could derive from the same root through different routes of formation. P. Canè adds, in descriptive terms, the possibility that it also meant "son of the Negro".

F. Miranda broadens the etymological picture by linking it with the Latin cognomen Niger and its medieval derivatives Nigrus, Negro and Nigro, and notes that the surname could also originate by aphaeresis of names such as Ranieri, Guarneri or Maineri. Miranda further adds a possible Hebrew root: Nerì, which means "my lamp, my light", used as a diminutive of Neriel ("my light is God"), a name that appears in the Gospel of Luke (3, 23–31) among the ancestors of Jesus.

The surname is diffused throughout Italy, with a greater frequency in Emilia-Romagna and Tuscany, and a presence also in Lazio, Lombardy, Sicily, Calabria, Umbria, Piedmont, Liguria, the Marche and Campania.