E. Rossoni notes that this surname derives directly, or through a hypocoristic, from the medieval name Toma, a variant of Tommaso, an Italianization of the Byzantine name Thomàs. The name is documented in Solofra, in the Avellino area, in the year 1500. Rossoni places its presence in the Salento area —that is, the southernmost zone of the Apulia region, in southern Italy—, in the Gargano, in the Carrara area and in the Piacenza area. He also records the form Tomacci, almost unique, in the Potenza area.

R. Brondolo agrees on the origin from Tommaso, which he describes as an apocope of that name, and adds that through aphaeresis related forms such as Maso, Masino and Masetti derive. Brondolo places this surname in northern Italy.