E. Rossoni proposes two hypotheses of origin for this surname. The first links it with the locality of Gardengo di Fontanelice, in the Bologna area, a possible place of provenance of the founders of the lineage. The second interprets it as a Lombard ethnic form derived from place names such as Guarda di Loiano or Guarda di Molinella, also in the Bologna area, or Guarda di Ro Ferrarese, in the Ferrara area. Geographically, Rossoni places it in the region of Emilia-Romagna: in the Bologna, Ferrara and Ravenna areas.

F. De Laurentiis proposes a different etymology: he considers that the surname could derive from gardingo, with the sense of "wary" ("cautious, circumspect"), applied as a nickname to the one who acted with caution so as not to be surprised or found at fault. This hypothesis refers to a semantic base of a behavioural character, independent of any place name.