The consulted works concur in tracing this surname to the place name Naples. E. De Felice adds that it may also derive from the demonyms napoletano or napolitano, which constitute its principal variants. This is consistent with the note found in Surnames in Italy, which records that the name originally indicated a person from Naples.

F. Miranda provides further etymological detail, specifying that Naples goes back to the ancient Latin Neapolis, itself a compound of the Greek terms néos ("new") and pólis ("city"). Miranda also contributes a notable historical observation: in Sicily, following the edict of 1492 that required Jews to convert to Christianity, many adopted the names of localities and cities as surnames, and Napoli was among those chosen.

E. Rossoni notes that the surname is diffused throughout southern Italy, while the variant Napolitano, though also present in that area, is concentrated especially in the area of Naples. Miranda broadens this geographic picture, documenting a presence across Sicily, Campania, Calabria, Lazio, Lombardy, Piedmont, Apulia, Liguria, Tuscany, and Sardinia, with a particularly dense distribution in Sicily, including the areas of Palermo, Agrigento, Catania, Messina, and Trapani.