Gold Medallion, 5th century, Sweden. Runic inscription translated as GADAFI, believed to be short for Gandalfi, "for Gandálf".
Gandálf was a legendary king of the petty kingdom of Álfheimr ("elf home" or "land between rivers") in what today is western Sweden and south-eastern Norway. A later king of Álfheimr by the same name (or possibly the same one with a mixup of history) was said by the sagas to be the maternal grandfather of Ragnar Lodbrok.
Tolkien, however, most likely got the name from a section of the Völuspá called the Dvergatal (the "Catalogue of Dwarves"), where it's listed as the name of a dwarf alongside other familar names like Durinn, Dvalinn, Bívurr, Bávurr, Bömburr, Nóri, Óinn, Þorinn (Thorin), Fíli, Kíli, Glóinn, Dóri, Óri and Eikinskjaldi ("oaken shield").
