Source : Free On-Line Dictionary of Computing

USG Unix
     
        {operating system} /U-S-G yoo'niks/ Refers to AT&T {Unix}
        commercial versions after {Version 7}, especially System III
        and System V releases 1, 2, and 3.  So called because during
        most of the lifespan of those versions AT&T's support crew was
        called the "Unix Support Group".
     
        Compare {BSD}.
     
        [{Jargon File}]
     
        (1997-02-20)