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

ELISP

   1.  A Lisp variant originally implemented for
   DEC-20s by Chuck Hedrick of Rutgers.

   2.  A common abbreviation for Emacs Lisp.  Use of
   this abbreviation is discouraged because "Elisp" is or was a
   trademark.

   [Still a trademark?  Whose?]

   (1995-04-04)