An English hill in Ceredigion, a county in Wales, near the village Llanilar which is located close to the town of Aberystwyth.
This is the site of the last stand of the piglet Grugyn Silver Bristle, after whom the hill was evidently named. During the epic hunt of Twrch Trwyth, Arthur’s warriors pursued Grugyn Silver Bristle here and killed him, but Rhuddfyw Rhys and many other men were lost in the battle.
Notes
Garth, meant an enclosure, a buttress in old Welsh. The Persian gird, Norse garth, and the Anglo-Saxon yard, is a place girded round, or garded. Buarth, from bu, kine, and garth, a small enclosure, was situated on a hill in perilous times. Lluarth, from llu, a legion, and garth, enclosure, means an entranchment on a hill.
Source
Culhwch and Olwen | Late 11th century