G. Rohlfs places this surname in Calabria, with presence documented in the Lamezia Terme area, in the province of Catanzaro, and in localities such as Riace and Siderno, in the province of Reggio Calabria. He classifies it as of Greek-Byzantine origin and derives it from the expression kyr' Thomàs, composed of the Byzantine honorific treatment kyr- ("lord") and the name Thomas, with the sense of "lord Thomas".

P. Durante, on the other hand, proposes a different Greek origin: he links it to the term kertomeo, with the sense of "mocking". This etymology is independent of that proposed by Rohlfs and cannot be reconciled with it without forcing the sources.