The Free On-line Dictionary of Computing (19 January 2023):

DAU

   /dow/ [German Fidonet] D"ummster Anzunehmender User.  A German
   acronym for stupidest imaginable user.  From the
   engineering-slang GAU for Gr"osster Anzunehmender Unfall
   (worst foreseeable accident), especially of a LNG tank farm
   plant or something with similarly disastrous consequences.  In
   popular German, GAU is used only to refer to worst-case
   nuclear accidents such as a core meltdown.

   See cretin, loser and weasel.

   [Jargon File]

   (1994-12-06)


The Jargon File (version 4.4.7, 29 Dec 2003):

DAU
 /dow/, n.

    [German FidoNet] German acronym for Dümmster Anzunehmender User (stupidest
    imaginable user). From the engineering-slang GAU for Grösster Anzunehmender
    Unfall, worst assumable accident, esp. of a LNG tank farm plant or
    something with similarly disastrous consequences. In popular German, GAU is
    used only to refer to worst-case nuclear accidents such as a core meltdown.
    See cretin, fool, loser and weasel.