E. De Stefani proposes that this surname derives from the Germanic personal name Rupilo, an affectionate form of names composed on the bases hrothi ("fame," "victory") and behrta ("clear," "illustrious"), from which the Italian Roberto also derives. Over time, Rupp ceased to be felt as a diminutive and Rupilo was formed by means of the Germanic diminutive suffix -ilo. In the German and Bavarian areas, one called Ruprecht could receive the affectionate form Rüepel, which over time became a surname.

De Stefani places its historical presence in Prato Carnico, in the Carnia —a mountainous zone of northern Friuli, in the province of Udine—, especially in the localities of Pieria, Croce and Pesariis. According to this author, the bearers of the surname would have arrived in that region from present-day Austria, in particular from Styria, where a Magister Rupilus, a mason active in Prato Carnico from the beginning of the 16th century, is documented.

E. Rossoni, on the other hand, considers that the etymological origin is unknown. Rossoni records the surname in Friuli, with a presence in Prato Carnico, Tolmezzo and Udine, as well as in Gorizia and Trieste, in the Venezia Giulia area.