E. Rossoni proposes that this surname could derive from an aphaeretic form of names of Greek origin such as Agelao, Ermolao or Menelao, among others of the same kind. He notes that Lao is typically Sicilian, with a presence in Rosolini, in the Syracuse area, and in Palermo; while the variant Laò is practically unique and likewise of Sicilian origin.

V. Blunda offers a different explanation: he considers it a Sicilian surname of dialect origin, derived from the word làu, meaning "lake" or "pond", from the Latin lacus. The term was also applied to the seasonal pools of the island's interior. As a surname, it may have arisen from a microtoponym designating the inhabitant of a place close to one of these bodies of water in the local landscape.