What a strange name! I like the name Ethel, but I don't really like the '-dred' ending; it reminds me of the ordinary English vocabulary word 'dread' (to fear greatly; to anticipate with fear). :/
The only place I've seen this name is in the novel "The Daisy Chain" by Charlotte Mary Yonge. Etheldred is a very good character, and I like the name because it is unique. The book was great too! :)