The authors agree that the surname derives from a name of Germanic origin and that its figure of historical reference is Ferdinand III, king of Castile and León, canonised in 1671. V. Blunda specifies the etymology from the Germanic compound frithu-nanths, formed by frithu ("peace, truce") and nanths ("bold, valiant"), with the global meaning of "bold in peace". Blunda also highlights that Ferdinand III completed the great conquests of the Reconquista by taking Córdoba in 1236 and Seville in 1248, and that he definitively unified the crowns of Castile and León in 1230.

A. Bongioanni offers a different etymological reading, based on the Germanic elements her / hari ("army") and nand ("bold"), and notes that the name would have reached Italy probably through the Aragonese. Bongioanni also records the popular Tuscan form Fiordinando, with the affective diminutive Fiore, from which derived surnames such as Fiori, Fiorelli, Fioretti and Fiorini, as well as forms characteristic of the onomastics of Tuscany such as Belfiore and Biancofiore.