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

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 of redundant or superseded code.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?.


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

cruft
crufted

    (back-formation from "crufty") Anything unpleasant
   that accumulates over time.  Also used as a verb, as in cruft
   together, hand cruft.

   [Jargon File]

   (2006-01-19)