From Jargon File (4.3.1, 29 Jun 2001) :
cruft /kruhft/ [very common; back-formation from crufty] 1. n. An
unpleasant substance. The dust that gathers under your bed is cruft; the
TMRC Dictionary correctly noted that attacking it with a broom only
produces more. 2. n. The results of shoddy construction. 3. vt. [from
`hand cruft', pun on `hand craft'] To write assembler code for something
normally (and better) done by a compiler (see hand-hacking). 4. n.
Excess; superfluous junk; used esp. of redundant or superseded code. 5.
[University of Wisconsin] n. Cruft is to hackers as gaggle is to geese;
that is, at UW one properly says "a cruft of hackers".