F. De Laurentiis notes that this surname derives from Romanus.

F. Miranda broadens this origin and explains that Romanello is a hypocoristic —that is, an affectionate and diminutive form— of the name of Slavic origin Roman or of the Latin name Romanus. It can also derive from one of the place names containing the root roman-, such as Bassano Romano in the province of Viterbo, Casal Romano in the Mantua area, Fusine in Val Romana in the Udine area, or Roccaromana in the Caserta area. Given the wide presence of the surname in the Calabro-Sicilian area, Miranda also considers it possible that it comes from the dialect term rrumanieddu or rrumaneddu, which designates a "thin cord or string used by shoemakers or to make up parcels."

The surname is distributed in several regions of Italy, among them Veneto, Friuli-Venezia Giulia, Piedmont, Apulia, Lombardy, Sicily, Calabria, Campania and Liguria. In Sicily it is present in the Catania, Agrigento, Syracuse, Ragusa and Messina areas; in the Enna area it is documented in the localities of Centuripe and Catenanuova.