This came up, because I saw someone recently make the claim that Tolkien's depiction of Gandalf (and other wizards) using magical staffs has become a ubiquitous trope. No one could seem to recall an example of an older mythology or folk tale citing a wizard with a staff, but this seems hard to believe.
I looked for some evidence of Merlin being depicted as using a magical staff in an older text, like "Le Morte De Arthur", but didn't find anything in a cursory search, so I figured I would turn to this forum.
Are there depictions of Druids using magic staffs for example? Perhaps Eastern monks fighting with staffs taking on some legendary reputation?
Please tell me what there is to trace.
Thanks in advance!
Merlin - the quintessential European wizard takes heavy inspiration from preexisting myths about the chief magician of the Norse gods, Odin. (https://www.jstor.org/stable/25735286?seq=1 scholarly article detailing significant overlap in the Merlin/Odin myths) Odin is also often depicted with a staff, and Norse myth is reworked into Arthurian legend pretty readily. The sword Gram being shoved in a tree by Odin and only the rightful king could remove it is pretty clear as a predecessor to the "sword in the stone". (Source: The Volsunga Saga).
We first get reference to Odin being worshipped by the Germanic people in the 1st century in Tacitus' Germania where he was equated with Mercury. Austrian professor Rudolf Simek claims that there's some evidence of Odin already being depicted with his staff and his hat - which was partially why the Romans considered him analogous to Mercury. Odin is mentioned in old English magic, such as the Nine Herb Charm.
Another prominent figure that could contribute but has less of a direct lineage is Moses, being depicted as performing miracles by the raising of his staff. This would have grown in prominence as the Christianization of Europe commenced, but if Simek's claims are correct that Odin was already being shown with his staff in the 1st century then it's more likely that Moses' staff-wielding did not have as direct an impact on views of magic.
This last bit is speculation - It seems likely to me that various cultures would independently connect staffs with magic as the elderly were often the archetypes of the mystical.
But to directly answer your question - The wizard staff in European fiction is likely derived from depictions of Odin with a staff that influenced Merlin to have a staff and Merlin was used as the basis for future wizard characters.