The authors agree that this surname is peculiar to Sardinia and derives from the Logudorese term ardu, a variant of cardu ("thistle"), in turn from the Latin cardus. The Logudorese language is a macro-variety of Sardinian spoken in the interior of the island.

E. Rossoni documents the surname in Sardinia from medieval times: it appears among the signatories of the Peace of Eleonora of 1388, and also in the Condaghi of San Nicola di Trullas, San Pietro di Silki and Santa Maria di Bonarcado, monastic registers of the 11th to 13th centuries. Its presence is concentrated in the southwest of the island, especially in the Oristano area —localities such as Santu Lussurgiu, Pompu, Mogoro, Uras, Gonnosnò and Zerfaliu—, in the Cagliari area —Assemini and Sestu— and in the Medio Campidano region.

F. Miranda specifies that the origin would be a nickname linked to the cultivation or sale of thistles by the first bearer. Miranda also notes that in the Logudorese dialectal series the terms ardu – cardu – cadru – gardu – bardu all refer to the same plant. Outside Sardinia, the surname has minor presence in Lazio, Lombardy, Piedmont, Liguria, Tuscany and Veneto, as well as in Sicily, where it is recorded in the Palermo and Enna areas.