E. Rossoni and V. Blunda differ on the origin of the surname.

Rossoni suggests that they could derive from a contraction of the Latin name Raulus, an apocopated form of Raulandus. He notes that the Rao are mentioned among the noble lines of Sicily.

Blunda, on the other hand, for the Sicilian variant derives it from the Germanic compound Rad Wulf, with the meaning of "wolf of the counsel" or "counselling wolf," formed from rad ("counsel, deliberation") and wulf ("wolf").

Blunda notes that the association between prudent counsel and the totemic animal reflects the complexity of the Germanic anthroponymic ideal, which linked the reflective wisdom of the chief with the martial ferocity of the warrior as complementary aspects of legitimate power. He adds that the form Rao, with the loss of the intermediate consonants, is proper to medieval southern Italian.