The sources differ both on the geographical origin and on the etymology of this surname.

E. Rossoni considers it proper to the Bari area and links it to the place name Loseto, the name of an outlying district of that city. That district was an independent municipality in the 12th century, known then as Lusitum, and became a hamlet of Bari by decree in 1937. The surname would be, on this reading, an Italianized form of that local place name.

V. Blunda, by contrast, considers it a Sicilian surname of dialect origin and derives it from the word alosètu, which designates an almond grove or a spot planted with almond trees. The almond, introduced in ancient times, prospered especially in southern Sicily. As a surname it would have arisen from a microtoponym applied to the owner or worker of a plot with that characteristic.

Both proposals are compatible with an independent origin in each region: one linked to an urban place name in the Bari area, in Puglia, and the other to a term of the agricultural landscape in Sicily.