The authors agree that this surname derives from the demonym sardo, which designates the inhabitant or native of Sardinia.

E. Rossoni notes that the forms of the group —Sardi, Sardo, Sardone and Sardoni— all derive, directly or through augmentative forms, from that demonym, and indicates their geographic distribution: Sardi is concentrated in Liguria, Piedmont, Tuscany and Lazio; Sardo is typical of Campania, Sicily, Liguria and Piedmont; Sardone presents an important zone in the province of Bari and in Basilicata, especially in the Matera area, besides a smaller nucleus in Sicily; Sardoni, very rare, would seem to be proper to Rome.

E. De Felice does not develop the variants of the group, but specifies the original meaning of the ethnic: "inhabitant or native of Sardinia."