The authors differ on the origin of this surname, providing complementary interpretations according to the region of analysis.

E. De Stefani proposes that, in the Friuli area, the surname does not derive directly from the geographical term monte, but from a Friulian hypocoristic form of the given name Raimondo: the form Mont, equivalent to the Italian Mondo, arisen by apocope of (Rai)mondo. This name comes from the Germanic, composed of ragan ("counsel", with the sense of "divinity") and munda ("protection"), meaning "the one who protects with divine counsel". Over time the connection with the Germanic name was lost and the form Mont was reinterpreted as "mountain" or "hill", giving rise to the Italianized form De Monte, which finally became a surname. De Stefani documents it in Socchieve from the end of the 14th century and records it in localities of the Carnia, the northern mountainous zone of the province of Udine, such as Tolmezzo, Forni di Sotto, Ampezzo and Socchieve.

E. Rossoni, on the other hand, interprets the surname in a direct geographical sense: it would indicate a provenance of the founding ancestors from mountain zones. Rossoni documents different formal variants with a differentiated regional distribution: De Monte in Friuli —in localities such as Artegna, Ragogna, Udine, San Daniele del Friuli, Ampezzo and Buia—, as well as in Trieste and in the region of Puglia, in localities such as Nardò, Lecce, Mola di Bari, Taranto and Brindisi. He also records Demonte in the Turin area, in Mola di Bari and in the Foggia area; Demonti in the zone between Brescia and the Trentino-Alto Adige; De Monti in the Valtellina; and the Sardinian variants Demontis and De Montis, the latter present in the Cagliari area, Rome and Genoa.

The surname presents, consequently, multiple independent clusters of origin (ceppi), arisen in different regions without direct relation between them, with an etymological interpretation that varies according to the area: hypocoristic in Friuli, according to De Stefani, and geographical in the rest of Italy, according to Rossoni.