In Welsh oral tradition, Peredur and Gwrgi were killed fighting Eda Great-Knee at Caer Greu, after their warriors abandoned them.
The name may be a variation of Caer Creu, meaning “city of blood.”
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
Triads of the Island of Britain (Welsh ”Triads”) | 11th century to 14th century