The authors differ both in the geographical origin and in the etymology of this surname. E. Rossoni places it as peculiar to Sardinia and proposes two hypotheses: that it derives from a Sardinian dialectal modification with consonantal reduplication of the term fada ("fairy"), or from a nickname arisen from the Sardinian dialectal word fadda ("error, fault"). Rossoni notes that the etymology is uncertain and documents an earlier form, Falla, recorded among the signatories of the Peace of Eleonora (1388).

V. Blunda, on the other hand, considers it a Sicilian surname of Germanic root, derived from the personal name Falda, a Lombard anthroponym linked to the root fald ("fold, layer"). Blunda maintains that the duplication -dd- with simplification of the Germanic consonantal group is characteristic of southern Italy and of Sardinian, and attributes its diffusion in those zones to the medieval repopulation and to the migratory movements of the medieval period.

Both proposals agree in recognising that the surname reached its greatest rooting in Sardinia, although they differ on whether that prominence is explained by a strictly insular origin or by an expansion from the southern Germanic anthroponymy.