Llyn Cwm Llwch both Pen y Fan and Corn Du and indeed from the spur of Pen Milan to its west. Llyn Cwm Llwch Llyn Cwm Llwch () is a small lake or pool in the Brecon Beacons National Park in Powys, Wales. It is between 1 and 2 acres: much smaller than the two glacial lakes in the west of the Black Mountain (range): Llyn y Fan Fawr and Llyn y Fan Fach. It is of glacial origin, occupying a rock hollow beneath the peaks of Pen y Fan and Corn Du in the central Brecon Beacons. It is drained by the
Pen-y-ghent language, exactly as in today's Welsh, "Pen" meant 'top' or 'head', and "y" is most likely the definite article ("the"), exactly as in Modern Welsh "y". These elements are common in placenames throughout the island, and especially in Wales (compare Penyberth 'end of the hedge/copse', or Penyffordd 'head of the road/way', etc.). The element "ghent" is more obscure, however: it could be taken to be 'edge' or 'border'. The name "Pen-y-ghent" could therefore mean 'Hill on the border' (compare Kent). Alternatively, "ghent" could mean 'wind' or 'winds' – from the closest Welsh transliteration, "gwynt" ('wind'). Thus it might mean simply