River Wye given a Latin name "Vaga", an adjective meaning 'wandering'. The Tithe map references a Vagas Field in both Whitchurch and Chepstow. Philologists such as Edward Lye and Joseph Bosworth in the 18th and early 19th centuries suggested an Old English derivation from "wæg", "wave". The source of the Wye is in the Welsh mountains at Plynlimon. It flows through or past several towns and villages including Rhayader, Builth Wells, Hay-on-Wye, Hereford (the only city on the River Wye), Ross-on-Wye, Symonds Yat, Monmouth and Tintern, meeting the Severn estuary just below Chepstow. Its total length is . The lower of the
England–Wales border then runs westwards to the River Teme, and follows the river southeastwards through Knighton before turning south towards the River Lugg at Presteigne, which is within Wales. The boundary continues southwards across hills to the River Wye, and follows the river upstream for a short distance to Hay-on-Wye, on the Welsh side of the border. It continues southwards and rises through and across the Black Mountains, following the Hatterall Ridge past Llanthony on the Welsh side and Longtown on the English side, to reach the River Monnow near Pandy. It then generally follows the river, past Pontrilas (in England) and