From http://www.takeourword.com

"When sitting at your computer, waiting for it to boot up, had you ever wondered where this strange term comes from? Those of you who remember those far-off days when computers with the power of a pocket calculator needed their own building and ran programs consisting of holes punched into paper-tape may also remember that the earlier phrase was to bootstrap. Now the meaning becomes more apparent. When the computer was switched on, a built-in program executed which "pulled [the machine] up by its own bootstraps". This phrase, in turn, comes from a passage in the fantasy novel "The Adventures of Baron von Munchhausen" wherein the boastful Baron describes how he evaded the Turkish army by using this novel technique to scale the mirror-like face of a sheer cliff."