Adur

The connexion of the Welsh *ydwr* with the Greek ‛υδορ is remarkable. Can any of your readers tell me whether there be not an older Welsh word for *water*? There are, I know, two sets of Welsh numerals, of which the later contains many Greek words, but the older are entirely different. Is not *cader* akin to καθεδρα, and *glas* to γλαυκος?