Source : Free On-Line Dictionary of Computing

mess-dos
     
        /mes-dos/ (Or MS-DOG, Messy-DOS, mess-dross, mess-loss,
        mush-dos) Derisory term for {MS-DOS}.  Often followed by the
        ritual banishing "Just say No!"
     
        Most hackers (even many {MS-DOS} hackers) loathe {MS-DOS} for
        its single-tasking nature, its limits on application size, its
        nasty primitive interface, and its ties to {IBM}ness (see
        {fear and loathing}).
     
        In Ireland and the UK it is sometimes called "Domestos" after
        a brand of toilet cleanser.
     
        [{Jargon File}]
     
        (1994-11-16)