Using both the CTRL and META keys. “The command to burn all LEDs is double bucky F.”
This term originated on the Stanford extended-ASCII keyboard, and was later taken up by users of the space-cadet keyboard at MIT. A typical MIT comment was that the Stanford bucky bits (control and meta shifting keys) were nice, but there weren't enough of them; you could type only 512 different characters on a Stanford keyboard. An obvious way to address this was simply to add more shifting keys, and this was eventually done; but a keyboard with that many shifting keys is hard on touch-typists, who don't like to move their hands away from the home position on the keyboard. It was half-seriously suggested that the extra shifting keys be implemented as pedals; typing on such a keyboard would be very much like playing a full pipe organ. This idea is mentioned in a parody of a very fine song by Jeffrey Moss called Rubber Duckie, which was published in The Sesame Street Songbook (Simon and Schuster 1971, ISBN 0-671-21036-X). These lyrics were written on May 27, 1978, in celebration of the Stanford keyboard:
Double bucky, you're the one!
You make my keyboard lots of fun.
Double bucky, an additional bit or two:
Control and meta, side by side,
Augmented ASCII, nine bits wide!
Double bucky! Half a thousand glyphs, plus a few!
I sure wish that I
Had a couple of
Set of pedals to
Make the number of
Double double bucky!
Double bucky, left and right
OR'd together, outta sight!
Double bucky, I'd like a whole word of
Double bucky, I'm happy I heard of
Double bucky, I'd like a whole word of you!
— The Great Quux (with apologies to Jeffrey Moss)
[This, by the way, is an excellent example of computer filk —ESR] See also meta bit, cokebottle, and quadruple bucky.