in Literature

Where Did Odysseus Enter the Underworld?

In his first book against Rufinus, Claudian places Odysseus’ meeting with the shades of the dead in Gaul–or, rather, shows that he is familiar with a tradition that places the event there (fertur):

Est locus extremum pandit qua Gallia litus

Oceani praetentus aquis, ubi fertur Ulixes

sanguine libato populum movisse silentem.  (In Rufinum 1.123-5)

Does anyone know the antecedent for this tradition locating the event, not just at the edge of the world, but precisely in Gaul? I don’t recall coming across this before, but that presumably just shows my ignorance. Is this found anywhere in the mythographical tradition?