The authors agree that this surname has as its base the medieval name Romeo, derived from the Greek Rhomaios, a demonym of Rome that meant "Roman, citizen of Rome." In the Middle Ages, this term gradually acquired a new sense: that of "pilgrim," to designate those who travelled on pilgrimage, especially to Rome, in a way equivalent to the name Pellegrino.

F. De Laurentiis specifies that the Greek etymon operated in two distinct semantic directions according to the region. In the far south of Italy —Calabria and Sicily—, the surname points back mainly to the original sense of Rhomaios as "Roman of the East, Byzantine," given that in the Greek-Byzantine world the term also designated the inhabitants of Néa Rhóme, that is, Constantinople. On the other hand, in the north, the centre and other zones of the south of Italy, the surname derived from the later medieval sense of "pilgrim who has been to the Holy Land or to Rome."

F. Miranda broadens this duality by noting that the surname could also allude to pilgrims through the Latin expression Romam eo ("I go to Rome") or to the crusading knights who departed from Rome (ex Roma eo, "I depart from Rome"). Miranda further underlines its extended presence in almost all the regions of Italy, with a greater concentration in Calabria —especially in the Reggio Calabria, Catanzaro and Cosenza area— and in Sicily, where it appears in all the provinces with a special frequency in the Catania, Messina, Palermo, Trapani, Syracuse and Agrigento areas.

G. Rohlfs studies it as a surname of Greek-Byzantine origin in the context of southern Italy, with a presence documented in Lecce, in the province of Brindisi and in the province of Taranto. According to Rohlfs, it reflects the Byzantine identity in that area, in line with the sense of romaios as the designation that the Greeks of the East used to refer to themselves.

A. Bongioanni gathers the hypothesis of the scholar Zambaldi according to which Romeo could be a reduction of Borromeo, interpreted as Buon Romeo ("good pilgrim"). From this same origin would derive the surnames Borromeo and Borromini, characteristic of Lombardy and Piedmont. E. De Felice agrees with Bongioanni on the general etymology and highlights the very high frequency of the surname in southern Calabria, where it is the most frequent in Reggio Calabria, and in Sicily.