The consulted works concur in deriving this surname from the place name Nicolosi, a locality in the area of Catania, in Sicily. This point of agreement is shared by E. De Felice, E. Rossoni, and the reference work Surnames in Italy, which likewise traces it to the Sicilian town of that name.

F. Miranda broadens the picture by tracing the place name itself to the Benedictine monastery of San Nicola, founded in 1359 in the territory of Mount Etna, around which the urban settlement that eventually lent its name to the locality later developed. Miranda also provides the underlying etymology: the personal name Nikòlaos, from Greek, is a compound of nike ("victory") and leòs ("people, multitude"), Latinized as Nicolaus, with the overall meaning of "victor among the people."

On the geographic distribution of the surname, Miranda notes that it is typically Sicilian and is found across all provinces of the island, with the greatest concentration in the areas of Catania, Palermo, Messina, Trapani, Agrigento, and Syracuse. Beyond Sicily, it appears in specific, localized areas of Lombardy, Lazio, Piedmont, Tuscany, Emilia-Romagna, Liguria, Campania, and Calabria.