The authors agree that the surname derives from sega ("saw, sickle") or from the verb segare ("to cut with the saw, to reap"), and that it is linked to nicknames or trades related to woodwork or to reaping.

E. De Felice notes that the surname encompasses several derived forms: segantino, proper to Veneto, Emilia-Romagna, Tuscany and central Italy; segato, of Veneto; and segatore ("one who cuts trees and wood with the saw; one who works in a sawmill"). Some Venetan surnames could also derive from the place names Séga (in the Verona, Treviso and Venice areas) or Séghe (in the Vicenza area).

E. Rossoni identifies different independent lines of origin (ceppi): one between Trentino and the Verona area, another between the Rovigo and Ferrara areas, and a third between the Viterbo and Rome areas. Rossoni further points out that the surname could have arisen from apocopated forms of medieval names such as Segafredus, which adds an alternative path of origin to the purely professional one.