The authors agree that the surname could derive from apocopated forms of medieval names such as Morando, or from Renaissance contracted forms of the name Rinaldo. F. Miranda broadens this hypothesis and notes that it could also be a diminutive of the name Rando, in turn a hypocoristic of Morando, Bertrando or Randolfo, with a Germanic root in rand ("edge") or randa ("shield"). The same author adds that in Italian randello designates a thick stick used to strike, which could have given rise to a nickname turned into a surname.

E. Rossoni details the geographic distribution of the surname and its variants. Randelli presents areas of concentration in Florence and Scandicci, in Prato and Carmignano, in Rome, and smaller nuclei in Cerchiara di Calabria —in the Cosenza area— and in Troina, in the Enna area, Sicily. The variant Randellini is characteristic of the Arezzo area, with a presence in Arezzo and Civitella in Val di Chiana. The variant Randello is typically Sicilian, native of Licodia Eubea, in the Catania area. Miranda further specifies that the surname is documented in some sixty-five Italian localities, mainly in Tuscany, Sicily, Lazio and Lombardy, with a smaller presence in Campania, Calabria, the Marche and other regions.