WordNet (r) 3.0 (2006):

cookie jar
    n 1: a jar in which cookies are kept (and sometimes money is
         hidden) [syn: cookie jar, cooky jar]

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

cookie jar
 n.

    An area of memory set aside for storing cookies. Most commonly heard in
    the Atari ST community; many useful ST programs record their presence by
    storing a distinctive magic number in the jar. Programs can inquire after
    the presence or otherwise of other programs by searching the contents of
    the jar.


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

cookie jar

   1.  An area of memory set aside for storing
   cookies.  Most commonly heard in the Atari ST community;
   many useful ST programs record their presence by storing a
   distinctive magic number in the jar.  Programs can inquire
   after the presence or otherwise of other programs by searching
   the contents of the jar.

   2.  A cracker term for the password file of a
   multi-user computer.

   [Jargon File]

   (1997-02-12)