Holy tradition states that Rupert was a scion of the Frankish royal Merovingian dynasty;[3] he was possibly related to the Robertians, and likely a descendant of Count palatine Chrodbert II.

[4] As bishop at Worms, Rupert was first accepted as a wise and devout dignitary, but the mostly pagan community came to reject him and forced him out of the city by the end of the 7th century.

The Agilolfing duke Theodo of Bavaria requested that he come to his residence at Regensburg (Ratisbon) to help spread the Christian faith among the Bavarian tribes.

Here, he stayed at Lorch, the former Roman city of Lauriacum (today part of Enns), where an early Christian church—the present Basilica of St. Lawrence—already existed.

Instead, he proceeded along the Roman road via Seekirchen to the ruined city of Juvavum, which he made his base and renamed "Salzburg" (Latin: Salisburgum).