the word dïc already existed and was pronounced ("deek") in northern England and ("deetch") in the south. The origins of the word lie in digging a trench and forming the upcast soil into a bank alongside it. This practice has meant that the name dïc was given to either the excavation or the bank, and evolved to both the words "dike"/"dyke" and "ditch".

Thus Offa's Dyke is a combined structure and Car Dyke