The authors agree that this surname derives from the personal name of Germanic origin Siccardo or Sicardo, attested in Italy from the 8th century. E. De Felice explains that the name goes back, with a probably Lombard but above all Frankish tradition, to a compound etymon: *sigu- (in Gothic sigis, in Old High German sigu: "victory") and *hardhu- ("hard, strong"), with the possible original meaning of "strong in victory." The name was in use throughout the Middle Ages.

E. Rossoni specifies that the surname Siccardi is typical of Piedmont and central-western Liguria, with a small presence in the Brindisi area, while Siccardo, very infrequent, seems specific to the Savona area. Both forms would derive from the medieval name Latinized as Sicardus or Siccardus. Rossoni documents a Sicardus bishop of Novara in the 8th century, its presence in the Bologna area in 1292, and a notary named Bernardino Siccardi in the Turin area in the 16th century.

De Felice adds that abbreviated forms such as Sicca and Sicco, proper to Piedmont and Liguria, and Sica, frequent in the region of Campania, would be reduced variants of the same name of origin.