E. Rossoni distinguishes several forms of this surname according to their geographic distribution in Sicily. The variants Schiliro and Schilirò are proper to the Catania area, with a presence documented in localities such as Bronte, Catania, Maletto, Adrano and Paternò. The forms Schilliro and Schillirò, much rarer, also appear in that same zone. Schirò, on the other hand, is characteristic of the Palermo area, while Schiros, equally rare, is again located in the Catania area.

As to the origin, Rossoni notes that all these variants are of Greek root, although for Schirò and Schiros he also contemplates the possibility that they derive from the place name Skyros, an island of the Sporades archipelago. He cites G. Rohlfs to hold that they would derive from the Greek adjective skliròs ("hard"), a form that survives as a surname in Greece itself. Rohlfs, for his part, specifies that it is a surname of Greek-Byzantine origin, and records its presence also in Taranto, placing it within the onomastic family of Schirò. The Greek form he documents is sklērós, with the meaning of "hard," and he notes that in Greece it survives as Skliròs.

G. P. Holmes agrees on the meaning —"hard, strong"— and on the Greek root, although he characterizes the surname as of Albanian origin with a Greek etymon, without developing this distinction. Holmes further mentions that Schiliro figures among the most frequent surnames in the commune of Bronte, a fact that reinforces the geographic concentration noted by Rossoni in that locality of the Catania area.