Drewyn Gawr made Caer Drewyn in Deyrnion, the other side of the river from Corwen. And to his sweetheart he made that Caer, to milk her cows within it.
From ‘The Giants of Wales and their Dwellings’ by Sion Dafydd Rhys, c.1600. Gawr = a giant (because you’d need to be a giant to build something like Caer Drewyn. Maybe they were even giant cows?). The 1917 translation by Hugh Owen is at the Celtic Literature Collective here:
maryjones.us/ctexts/giants_wales.html