The meaning of the English place-name Redcar is 'reedy bog' according to all the reference books I have - it's Anglo- Saxon, possibly with some Scandinavian influence. I think 'boggy or swampy ground' is the most likely explanation of your East Dereham instance. Celtic placenames are extremely rare in East Anglia, so the derivation from Welsh. Brythonnic 'caer' is most unlikely in that part of Britain. My best guess for Stey is that it is a regional form of the common AS element 'stow(e)', which means simply 'place'. Elsing Stey would be (something like) 'the place of Elsi's people', where Elsi is a proper name. Ian