The authors differ both on the geographical origin and on the etymology of this surname. E. Rossoni considers it very rare and probably originating in the Varese area, in Lombardy. He proposes that it could derive from the Latin gens Aquilia, linking it to the notary Bernardus Guila de Thoyrio, active towards the end of the 14th century in Savoy. Rossoni also mentions, though as a less likely hypothesis, a derivation from the place name Guiglia, a locality in the Modena area.

V. Blunda, by contrast, proposes a Germanic origin, and presents it as a surname of Sicilian root. He derives it from the personal name Wilia, a feminine or hypocoristic form linked to the root wil ("will", "desire"), with the palatalization characteristic of southern Italian. According to Blunda, the root wil appears as the first element in numerous European compounds —such as Guglielmo, Vilfredo or Wilibald— associated with the Germanic ideal of the will as a quality of the free man. He notes that the surname survives both in Alpine areas of northern Italy and in regions where medieval resettlement introduced Lombard personal names.