Jacob Schmid, who had published an extensive collection of saint legends in the 18th century, including the Legend of Arnoldus, also questioned Arnold's Greek origins and suggested instead that he came from Raetia, an ancient Roman province reaching from the north of present-day Italy to the south of present-day Switzerland.

In an imprint of the Acta Sanctorum of the Bollandists from 1725, the death of Arnold was assumed to have occurred at the beginning of the 9th century; in Stadler's Complete Lexikon of Saints of 1840 it is restated that he died around 800.

[3] Between 922 and 1168, his death and burial place was renamed after his name into Arnoldsweiler (wilre sancti Arnoldi), which today forms a district of Düren.

In addition to a document from 1339, there only is an express earliest mention of his person in the transcript of his Vita, so only about 500 years after his death.

As little documentary evidence exists in writing, it cannot be determined with certainty how far Saint Arnold's biography is based on real facts, or if with the passage of time it was interlaced with legends.

Arnold accompanied Emperor Charlemagne and his entourage on hunts in the Bürgewald (a forest area north of Düren between Aachen and Cologne, bordered by the rivers Rur and Erft).

Arnold challenged the emperor in a bet to give him as much forest land as he could circle on horseback while the banquet lasted.

The crafty Arnold arranged for fresh horses in the surrounding villages and managed to circumnavigate the entire forest before the meal was over.

The horse then scraped the ground with its hoof and a spring of water arose that still bears the name Arnolduspötzsche (Arnoldusquelle/Saint Arnold Fountain) today.

One day he gave alms to the poor in the village and they brought their benefactor a fish from the market that had swallowed a ring.