The Free On-line Dictionary of Computing (30 December 2018):

Devil Book

    "The Design and Implementation of the 4.3BSD
   Unix Operating System", by Samuel J. Leffler, Marshall Kirk
   McKusick, Michael J. Karels, and John S. Quarterman
   (Addison-Wesley Publishers, 1989, ISBN 0-201-06196-1).

   The standard reference book on the internals of BSD Unix.
   So called because the cover has a picture depicting a little
   devil (a visual play on daemon) in sneakers, holding a
   pitchfork (referring to one of the characteristic features of
   Unix, the "fork(2)" system call).

   [Jargon File]

   (1996-12-03)