The authors agree that this surname derives from the gentilic "Calabrian", from the Greek form kalabròs or Kalavròs, which designated the inhabitant of Calabria. Its origin is therefore Greek-Byzantine.

E. Rossoni notes that the variant Calabro is typical of the Salento area —that is, the southernmost zone of the Puglia region, in southern Italy—, while the accented variant Calabrò presents a main cluster in Sicily, with presence also in the Reggio Calabria and Cosenza areas. He adds a relevant historical fact: in Roman times, the Salento was called Calabria, which would explain the use of the gentilic in that area geographically distant from present-day Calabria.

G. Rohlfs broadens the distribution by noting that the surname is present throughout Calabria, in the Naples area and is very frequent in Sicily. P. Durante agrees on the Greek origin of the surname, without adding additional information.