What is "llygadwy"

Llygadwy is a locality near the village of Bwlch in the county of Powys in southeast Wales. The usual meaning of llygad in Welsh is 'eye' but it can signify a spring e.g. Llygad Llwchwr. The name therefore signifies the source of a stream known traditionally as 'Yw' though which is nowadays known as Ewyn Brook and which flows through a wide, though short, vale known traditionally as Ystradyw. The modern spelling appears to be a corruption of an earlier form Llygadyw. The spring arises where a band of non-marine limestone known as a calcrete outcrops within countryside otherwise dominated by sandstone rocks of the Old Red Sandstone.