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

quadruple bucky
 n. obs.

    1. On an MIT space-cadet keyboard, use of all four of the shifting keys
    (control, meta, hyper, and super) while typing a character key.

    2. On a Stanford or MIT keyboard in raw mode, use of four shift keys
    while typing a fifth character, where the four shift keys are the control
    and meta keys on both sides of the keyboard. This was very difficult to do!
    One accepted technique was to press the left-control and left-meta keys
    with your left hand, the right-control and right-meta keys with your right
    hand, and the fifth key with your nose.

    Quadruple-bucky combinations were very seldom used in practice, because
    when one invented a new command one usually assigned it to some character
    that was easier to type. If you want to imply that a program has
    ridiculously many commands or features, you can say something like: ?Oh,
    the command that makes it spin the tapes while whistling Beethoven's Fifth
    Symphony is quadruple-bucky-cokebottle.? See double bucky, bucky bits,
    cokebottle.


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

quadruple bucky

   Obsolete. 1. On an MIT space-cadet keyboard, use of all four
   of the shifting keys (control, meta, hyper, and super) while
   typing a character key.

   2. On a Stanford or MIT keyboard in raw mode, use of four
   shift keys while typing a fifth character, where the four
   shift keys are the control and meta keys on *both* sides of
   the keyboard.  This was very difficult to do!  One accepted
   technique was to press the left-control and left-meta keys
   with your left hand, the right-control and right-meta keys
   with your right hand, and the fifth key with your nose.

   Quadruple-bucky combinations were very seldom used in
   practice, because when one invented a new command one usually
   assigned it to some character that was easier to type.  If you
   want to imply that a program has ridiculously many commands or
   features, you can say something like: "Oh, the command that
   makes it spin the tapes while whistling Beethoven's Fifth
   Symphony is quadruple-bucky-cokebottle."  See double bucky,
   bucky bits, cokebottle.

   [Jargon File]