E. De Felice notes that this surname is proper to southern and also central Sardinia, and that it was formed from the affectionate, familiar name Lòi, an abbreviation of Ballòi or Ballòe, Ballòre, a hypocoristic of Salvatore. In some cases, according to De Felice, it could also continue the Catalan and Spanish name Eloy, corresponding to Eligio, as a hypocoristic by aphaeresis.

E. Rossoni agrees on the Sardinian origin and on the derivation by aphaeresis from the Campidanese nickname Balloi, a hypocoristic of Sarbadori (Salvatore). Rossoni adds that, in certain cases, the surname could derive from place names such as Su Loi, a hamlet of Capoterra, in the Cagliari area. He also notes that among the signatories of the Peace of Eleonora of 1388 several bearers of the forms Loi and Loy appear.

E. De Stefani takes up a different etymological tradition, linked to northern Italy: in Friuli, the Latin name Eligius —related to the verb eligere ("to choose") and understood as "chosen by God"— gave rise to the forms Alò, Aloi and Loi, which in time became a surname. This variant is documented from the middle of the 16th century in Enemonzo, in Carnia, the mountainous area of the north of the province of Udine.