The authors agree that the surname was formed from the Greek term adelphós ("brother"), in the context of Christianity of Greek tradition.

E. De Felice specifies that these are Sicilian surnames formed from the personal names Adello and Adella, which continue the Latin names —late and of Greek-Eastern and later Christian milieu— Adelphus and Adelphia, and the Greek Adelphós and Adelphé, derived from adelphós ("brother") and adelphé ("sister"). He notes that these names took hold in Christian communities, especially of Greek tradition, with the new meaning of "brother, sister in Christ, in religious faith".

V. Blunda, for the Sicilian variant, derives it from the Greek etymon Adelphòs ("brother"). He notes that the root shares a lexical family with the Italian word fratello, of Latin origin, but retains the Hellenic cultural mark. He adds that in Byzantine Sicily the name was sometimes used as a monastic anthroponym, since the members of religious communities called one another "brothers" following the tradition of Eastern Christianity.