Source : Free On-Line Dictionary of Computing

second-system effect
     
        (Sometimes, more euphoniously, "second-system syndrome") When
        one is designing the successor to a relatively small, elegant,
        and successful system, there is a tendency to become grandiose
        in one's success and design an {elephantine} feature-laden
        monstrosity.  The term was first used by Fred Brooks in his
        classic "{The Mythical Man-Month}.  It described the jump from
        a set of nice, simple operating systems on the {IBM 70xx}
        series to {OS/360} on the 360 series.  A similar effect can
        also happen in an evolving system; see {Brooks's Law},
        {creeping elegance}, {creeping featurism}.  See also
        {Multics}, {OS/2}, {X}, {software bloat}.
     
        [{Jargon File}]