E. Rossoni notes that this surname is typical of Sicily, especially of the western part of the island: Alcamo in the Trapani area, Palermo, Cinisi and Partinico in the Palermo area, and the Agrigento area. According to Rossoni, it would be a surname of fairly recent origin, probably derived from a nickname related to the trade of the founding ancestor: impastato, referring to one who kneads dough.

V. Blunda agrees on the Sicilian and dialect origin, but specifies that the base form is 'mpastàtu, a participle designating someone who is "dirty, smeared or covered in mud or flour". On this reading, the nickname would not have alluded exclusively to the trade of kneading, but more broadly to any work that soils the body: the baker, the potter or the field labourer.