From The Free On-line Dictionary of Computing: (http://www.foldoc.org/, Editor Denis Howe)
/wab'it/ [almost certainly from Elmer Fudd's immortal line "You wascawwy wabbit!"] 1. A legendary early hack reported on a System/360 at RPI and elsewhere around 1978; this may have descended (if only by inspiration) from hack called RABBITS reported from 1969 on a Burroughs 55000 at the University of Washington Computer Center. The program would make two copies of itself every time it was run, eventually crashing the system.