What is "mathern"

Mathern (; older form: Merthyr Tewdrig) is a historic community (parish) and village in Monmouthshire, south east Wales, about south west of the town of Chepstow, close to the Severn estuary, the Bristol Channel and the M48 motorway. The village is designated as a Conservation Area. It is now bisected by the motorway, which passes over the road through the village, with the original village located to the south and the more recent development, known as Newton Green, to the north.