Deganwy is a small town in Conwy County Borough. It lies in the Creuddyn Peninsula alongside Llandudno and Rhos-on-Sea. Historically part of Caernarfonshire, it is located south of Llandudno and to the east of Conwy, which is on the opposite side of the River Conwy, and with which it forms the Conwy community. Indeed, the name Deganwy has been interpreted in modern times as Din-Gonwy, which would mean 'Fort on the River Conwy', but the historical spellings make it impossible for this to be the actual origin of the name (although mentioned in Domesday Book is 'the territory of the Decanae tribe'). The original wooden castle was rebuilt in stone after 1210 (NPRN 95282).
Source: https://en.wikipedia.org/wiki/Deganwy

RCAHMW, 21 August 2017