GAER, or Caer, any one of numerous places in Wales, Monmouth, and Cornwall, where there was an ancient British or a Roman camp. A conspicuous one, also called Caer-Bannau, is in the western vicinity of the town of Brecon; another is on the Julian way, near Tretower, in the E of Breconshire; another is in the vicinity of Blaenforth, in Cardigan; another is on the river Ithon, not far from Penybont, in Radnor; another is near Llwyngwril, in Merioneth; another is on the Julian way, 2 miles SW of Llanthoney abbey, in Monmouth; another is in the northern neighbourhood of Trelowarren, in Cornwall; and others, either called simply Gaer, or having prefixes or suffixes to that name, are in other places.

(John Marius Wilson, Imperial Gazetteer of England and Wales (1870-72))