The authors agree that the surname very probably has an ethnic origin, linked to the people of the Galatians —called by the Romans galli—, a population of Celtic origin that settled first in Thrace and, later, in the 3rd century BC, in a region of Asia Minor called Galatia. E. Rossoni also mentions the hypothesis of a derivation from the name of the Romanian city of Galați, although he rules it out as extremely improbable.

The authors likewise agree that the surname could derive from Italian place names: Galati, in the Reggio Calabria area, and Galati Mamertino, in the Messina area. F. Miranda adds as a possible referent the Miniera Galati, a necropolis of the Hellenistic period and an ancient sulphur mine located in Barrafranca, in the Enna area. For his part, G. P. Holmes notes that the surname comes specifically from Tortorici, a locality of the Messina area.

The three authors also agree on a third hypothesis: the derivation from a nickname of Greek root, from the term gàla ("milk"), referring to the trade of milkman exercised by the first bearer of the surname. Rossoni notes that the surname is especially spread in the southernmost zone of the region of Puglia, in Naples, in Calabria, and in Sicily. Miranda broadens this distribution to almost all the Italian regions.