Source : Free On-Line Dictionary of Computing

fepped out
     
         /fept owt/ The {Symbolics 3600} {LISP Machine} has a
        {Front-End Processor} (FEP).  When the main processor gets
        {wedged}, the FEP takes control of the keyboard and screen.
        Such a machine is said to have "fepped out" or "dropped into
        the fep".
     
        [{Jargon File}]
     
        (1994-12-01)