The authors agree in noting that this surname is characteristic of the Bergamo area, in the region of Lombardy, with a presence extending also towards the Milan area. E. Rossoni specifies that it derives from the place name Mazzoleni, a locality of the Valle Imagna, in the Bergamo area, and documents traces of its fixing as a surname from the 14th century, with a subsequent expansion towards the Milan area.

E. De Felice agrees on the toponymic origin, although he describes it more briefly as a Lombard surname formed from the place name Mazzoleni, in the Bergamo area.

The base would be the Germanic personal name Mazo, Latinized as Mazzus and documented from the 8th century, which evolved into Mazzolus and then into the present surname. The Valle Imagna, and in particular Costa Imagna, is held to constitute the core of origin of the surname, where it coexists almost exclusively with Macconi. It is further noted that the families are documented in Bergamo, Milan and Monza, as well as in Switzerland, and that in Italian the expected form would be Mazzolani.