How many words are there, that have the same letter pattern as "DGETGQSNUD"?
Ten-letter words, where the first and last letters are the same and the second and the fifth letters are the same?
I only know of three: "disfigured", "henceforth", and "secretions".
Pattern-word lists are your friend. It's pretty easy to make your own pattern word lists, with your desktop computer (which has the advantage of giving you files that can be computer-searched.) But if you're not up to that, Aegean Park Press sells a number of books containing pattern word lists. And there's a good set of pattern word tables in Appendix D of FM 34-40-2, which can be downloaded from the internet:
FM 43-40-2 Basic Cryptanalysis