Does anyone know what exactly the "Dfr" stands for, that is affixed to the names of the alternate versions of many, if not most, blackletter fonts (eg. Wilhelm Klingspor Gotisch, Goudy Text et al.)?

My guess is something like "Deutsch Fraktur", because these versions seem to have the long s required for authentic old-time German as well as Umlaut versions of A, O and U.

But then, knowing beats guessing, so if anyone knows for sure, I'd be most grateful.