DNR, n. and adj. The OED officially gives a 1983 use of the medical initialism, standing for do not resuscitate, as the first citation, but it includes a 1976 citation of DNR from the New York Times in brackets, although it’s not at all clear why brackets appear in the entry, which are generally used for foreign uses, prototypical forms, and uses not quite in the current sense.
My guess is that it’s because that first occurrence is a citation of a code used in hospital records rather than an actual use of the term.
I understood this to be “MUDD” multi-user dungeons and dragons
Not only have I never heard or seen this, but it doesn’t make any sense, because it’s the dungeon that is multi-user—the dragons are part of the name of the game, but not of this expression.