The authors agree that this is a toponymic surname derived from forms of the type somma or sommo, meaning "elevated locality" or "highest part of a place, a height or a road". It is present throughout Italy, with a greater concentration in the south of the country.

E. De Felice notes that the surname formed from place names of the Somma type, common with various determinations throughout Italy. Among especially representative compound forms he mentions Sommacampagna, in the Verona area; Sommariva, in the Cuneo area and in Genoa; and Sommavilla, also in the Veneto area.

E. Rossoni identifies at least three independent stems of origin: one in the Milan area, which would derive from the place name Somma Lombardo, in the Varese area; another in the Naples area, possibly linked to place names such as Massa di Somma or Somma Vesuviana; and a third in the Bari area.

E. De Stefani adds that in the Carnia —a mountainous region in northern Friuli, in the province of Udine— the surname is documented from at least the late 16th century, with a presence in Piano d'Arta and in Zuglio. He links it to an abbreviated form of the surname Sommavilla, a variant of Sonvilla, with which it shares the same motivation of orientation within the settlement. He also records the variant Summa, attested in southern Italy.