The river Mersey, Cheshire and Lancashire, recorded as the river Maerse in 1002AD, the word maerse is derived from the Old English Maeres-ae, which means boundary river. The river Penk, Somerset, the word penk comes from the Old Brythonic word penno, the Roman fort of Pennocrucium once stood on its banks, the word penk roughly means hill river. The river Derwent, Yorkshire, from the Old Brythonic river name Derventio, which is derived from the word derva, which means oak, and from the Welsh derw, the river where the oak trees grew, or where the oak trees were common. The river Wreak, Leicestershire, recorded as the river Werc in 1237AD, the word werc is derived from the Old Scandinavian word vrepk, which means wrathful and twisted because the Wreak is a very winding river. The river Witham, Leicestershire, recorded as the river Withma in 1150AD, this river was referred to by Ptolemy as the river Eidomanios, but the Old Brythonic word was Widumanios, the Widu part is derived from the Welsh gwydd, which means forest, the manios part is derived from the Latin word manare, which means to flow. The river Devon, Leicestershire, recorded as the river Dyvene in 1252AD, the word dyvene is derived from the Old Brythonic word dubona, which means black river. The river Glen, Leicestershire, recorded as the river Glenye in 1276AD, the word glenye is derived from the Old Brythonic word glano, which means holy and beautiful. The river Welland, Northamptonshire, first recorded as the river Weolud 921AD, the weolud is derived from the Old Brythonic and Celtic word vesu, which means good, the lud part is derived from the Old Irish word luaid which means to move. The river Nar, Norfolk, the word nar is derived from the Old English word nearu, which simply means narrow. The river Wensum, Norfolk, the word wensum is identical in meaning as the river Wantsum, Kent, which means in Old English, winding. The river Yare, Norfolk, first recorded as the river Gariennos, an Old Brythonic name taken from the Old British name for their fortress Garianno, which the Romans rebuilt, today it is known as Burgh Castle, parts of the Roman walls still stand. The river Thurne, Norfolk, derived from the Old English word thyrne, which means thorn-bushes, the river where the thorn-bushes grew.