Source : Free On-Line Dictionary of Computing

donuts
     
        (Obsolete) A collective noun for any set of memory bits.  This
        usage is extremely archaic and may no longer be live jargon;
        it dates from the days of {ferrite core memories} in which
        each bit was implemented by a doughnut-shaped magnetic
        {flip-flop}.
     
        [{Jargon File}]