The authors agree that this surname derives from the name of Germanic origin Franco (feminine Franca), documented from early stages of the Middle Ages. Its etymon is the Germanic *franka-, meaning "brave, bold; free". The name contains two intertwined values: on the one hand, an ethnic determinative ("belonging to the people of the Franks"); on the other, a determinative of political-social condition ("free man, with full rights").

E. De Felice notes that the name is documented from the 9th century as Francus and Franculus, and that its variants present a differentiated geographical distribution: Franco predominates in southern Italy; Franch and Frank appear in the Veneto; Francovich in Friuli-Venezia Giulia; the patronymic forms with De or Di are more frequent in Liguria; and La Franca is recorded in Sicily.

R. Brondolo, on the other hand, proposes an alternative etymology: he considers that the surname comes from Lanfranco, a Lombard name meaning "free man", with presence especially in northern Italy.