Note 34 — Chapter IX · Place-name Stories

A river may in Welsh be briefly called after anybody or anything. Thus in North Cardiganshire there is a stream called Einon, that is to say ‘Einion’s river,’ and the flat land on both sides of it is called Ystrad Einon, which looks as if one might translate it Einion’s Strath, but it means the Strath of Einion’s river, or of the stream called Einon, as one will at once see from the upper course of the water being called Blaen Einon, which can only mean the upper course of the Einon river. So here yw is in English ‘yew,’ but Ystrad Yw and Ỻygad Yw have to be rendered the Strath of the Yew burn and the Eye of the Yew burn respectively. It is moreover felt by the Welsh-speaking people of the district that yw is the plural of ywen, ‘a single yew,’ and as there is only one yew at the source somebody had the brilliant idea of making the name right by calling it Ywen, and this has got into the maps as Ewyn, as though it were the Welsh word for foam. Who began it I cannot say, but Theophilus Jones has it in his History of the County of Brecknock, published in 1809. Nevertheless the name is still Yw, not Ywen or Ewyn, in the Welsh of the district, though Lewis gives it as Ywen in his article on Ỻanvihangel-Cwm-Du. ↑