The Jargon File (version 4.4.7, 29 Dec 2003):

excl
 /eks'kl/, n.

    Abbreviation for ?exclamation point?. See bang, shriek, ASCII.


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

exclamation mark
!
excl
exclamation point
shriek

    The character "!" with ASCII code 33.

   Common names: bang; pling; excl (/eks'kl/); shriek; ITU-T:
   exclamation mark, exclamation point (US).  Rare: factorial;
   exclam; smash; cuss; boing; yell; wow; hey; wham; eureka;
   soldier; INTERCAL: spark-spot.

   The Commonwealth Hackish, "pling", is common among Acorn
   Archimedes owners.  Bang is more common in the USA.

   The occasional CMU usage, "shriek", is also used by APL
   fans and mathematicians, especially category theorists.

   Exclamation mark is used in C and elsewhere as the logical
   negation operation (NOT).

   (1998-09-17)