English folklore is largely drawn from Germanic, Celtic and Christian sources.

Mills suggests 'water' from a Celtic source, but gives no cognate.

One is forced to guess about Latin or French literary originals which are now lost, or upon continental lore that goes back to a Celtic source.

The Fionn poems form one of the key Celtic sources for the Arthurian legends.

Therefore, both the Latin and Germanic names were probably derived from a Celtic source, which would have been *Mosā.

We are thus thrown back upon Latin or French literary originals which are lost, or upon current continental lore going back to a Celtic source.

There is even an apparent Celtic source of the mysterious fisher king of the Grail romance.

Both of these details are unlikely to have been invented by a Roman or Celtic source.

The Vertigernus form may reflect an earlier Celtic source or a lost version of Gildas.

The theme of triple-death occurs in several places in medieval Celtic sources.