“Fairy Fortress”
Caer Feddwid, Caer Feddwidd, Caer Rigor
In the Welsh poem The Spoils of Annwn and a non-Arthurian poem in the Book of Taliesin – an alternative name for Caer Feddwidd, the Otherworld Fort of Carousal, which shares the same attribute of having a fountain that runs with wine.
Welsh tradition makes Arianrhod the ruler of Caer Siddi, though Arthurian legend does not seem to mention the name of the ruler on the occasion when Arthur and his men visited the mysterious fort.
Notes
Caer is a Welsh name for a wall or mound for defence – a city or castle wall, a fortress.
The root to this word might be cau, to shut up, to close, to fence, to enclose with a hedge. Cue means a field enclosed with hedges. When the Britons began to build cities they built a fortified wall to surround them, which were called caer.
The name Chester is a Saxonized form of the Latin castruni, a fort (and one of the few words recognised as directly inherited from the Roman invaders), is a common prefix and suffix in English place-names, such as: Colchester, Manchester, Chesterford, Chesterton. In the Danish and Anglian districts “Chester” is replaced with “caster,” such as: Doncaster and Lancaster, but both forms are allied to casirum, a Latinization of the Celtic caer.
Source
Preiddeu Annwfn | Attributed to Taliesin, c. 900