The authors agree that Naselli is a variant of the surname Nasello and shares its origin. According to the historiographers, the surname derives from a Lombard figure known as Palatino, nicknamed Nasello, son of King Liutprand, born around the year 738. E. Rossoni adds that its fixing as a surname is documented as early as the 12th century in Genoa, where Obertus Nasellus is recorded as chancellor in 1135.

F. Miranda notes that in some cases the surname could derive from the fixing as a surname of a nickname linked to the trade of the first bearer: that of fish seller, or else from the term nasello, a sea fish belonging to the family of the merluccidae —that is, the hake. Rossoni also mentions the possibility of an origin in a nickname, though without specifying its nature.

The surname is diffused mainly in Sicily, with a presence in the Catania, Palermo and Messina areas, as well as in inland localities such as Agira, Regalbuto and Nicosia. Miranda further notes cores —that is, specific areas of Italy where the surname is present— in Lombardy, Liguria, Piedmont, Tuscany, Emilia-Romagna, Lazio and Umbria.