Theophylact Simocatta
Bulgarian linguist Vladimir I. Georgiev proposed that the name was cognate to that of 6th-century South Slavic chieftain Ardagast, by way of metathesis. His name is attested in the works of Byzantine historian Theophylact Simocatta. If so, it would represent the "oldest attestation of the name", according to slavicist Heinrich Kunstmann (). However, Kunstmann also hinted at the possibility that the element "Arda-" could derive from the Thracian river Arda, and the name also reminded him of Gepid king "Ardaricus" and Roman general "Ardabur".