From the name of a place that includes the word "sasso" = stone, rock. Possibly also derived from the first name Sasso or Sassone, of German origin, to indicate someone from Saxony, population that came in Italy with the Lombards.

E. De Felice, E. Rossoni and F. De Laurentiis agree that the surname was formed from place names of the sasso group ("rock, boulder"), very common in all the Italian regions.

De Felice specifies that it includes forms such as Sasso and the corresponding Sassu in Sardinia (for example, Sassu Arborea, in the province of Oristano) and, in part, for the altered forms, Sassetta (in the province of Livorno) and Sassuolo (in the province of Modena). He adds that, for Sasso, Sassi and Sassetti, belonging to the Sasso surname group is also possible.

Rossoni distinguishes the forms and their geographic distribution: Sassi would be of the region of Emilia; Sasso would have several nuclei in Apulia, Campania, Veneto, Piedmont and Liguria. As examples of place names he cites Castel di Sasso, in the Caserta area; Isola del Gran Sasso, in that of Teramo; Madonna del Sasso, in that of Novara; and Sasso Marconi, in that of Bologna, among others.