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

cokebottle
 /kohk'bot?l/, n.

    Any very unusual character, particularly one you can't type because it
    isn't on your keyboard. MIT people used to complain about the
    ?control-meta-cokebottle? commands at SAIL, and SAIL people complained
    right back about the ?escape-escape-cokebottle? commands at MIT. After the
    demise of the space-cadet keyboard, cokebottle faded away as serious
    usage, but was often invoked humorously to describe an (unspecified) weird
    or non-intuitive keystroke command. It may be due for a second inning,
    however. The OSF/Motif window manager, mwm(1), has a reserved keystroke for
    switching to the default set of keybindings and behavior. This keystroke is
    (believe it or not) ?control-meta-bang? (see bang). Since the exclamation
    point looks a lot like an upside down Coke bottle, Motif hackers have begun
    referring to this keystroke as cokebottle. See also quadruple bucky.


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

cokebottle

    /kohk'bot-l/ Any unusual character,
   particularly one you can't type because it isn't on your
   keyboard.  MIT people used to complain about the
   "control-meta-cokebottle" commands at SAIL, and SAIL
   people complained about the "altmode-altmode-cokebottle"
   commands at MIT.  After the demise of the space-cadet
   keyboard, "cokebottle" was used less, but was often used to
   describe weird or non-intuitive keystrokes.

   The OSF/Motif window manager, "mwm" keystroke for
   switching to the default keybindings and behaviour is
   control-meta-bang.  Since exclamation mark might be
   thought to look like a Coke bottle, Motif hackers referred
   to this keystroke as "cokebottle".

   See also quadruple bucky.

   [Jargon File]

   (1995-01-04)