The authors agree that the surname derives from an Italianization of the Spanish García, by a process of metathesis —the phenomenon whereby two sounds within a single word swap places— which transforms the initial syllable Gar- into the form Gras-. The double s answers to a phonetic adaptation of the Spanish c. E. Rossoni notes that the surname could be of Spanish origin, with possible Judaeo-Sephardic influence. The variants Garsia, Ingarsìa and Ingrassìa share this same etymon.

Rossoni documents a presence of the surname between the Naples and Caserta areas, and also in the Catania area. F. Miranda broadens this geographical picture and indicates an extended distribution covering Campania, Sicily, Lombardy, Piedmont, Lazio, Tuscany, Liguria, Emilia-Romagna and Calabria. In Sicily he records a presence in the provinces of Catania, Agrigento, Messina and Palermo, with several comuni documented in the Enna area.

G. P. Holmes proposes a different etymology, of Greek origin, with the meaning "oblique" or "transverse", although he presents it with reservations. This hypothesis finds no support in the other sources consulted.