What is "striguil"

Striguil or Strigoil is the name which was used from the 11th century until the late 14th century, for the port and Norman castle of Chepstow, on the Welsh side of the River Wye which forms the boundary with England. The name was also applied to the Marcher lordship which controlled the area in the period between the Norman conquest and the formation of Monmouthshire under the Laws in Wales Acts 1535–1542.