Caer Feddwid, Caer Feddwidd, Caer Siddi
An alternative name for Caer Feddwidd, which is also known as Caer Siddi, or the Fort of Carousal.
Though Welsh tradition states that Caer Feddwidd contains a fountain that runs with wine, and no one there knows old age, this variant would seem to suggest a realm of the dead from which there is no return.
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