Cruft
1. Trash, debris, or other unwanted matter that accumulates over time.
2. Unnecessary digital information that accumulates over time, such as unneeded files or obsolete lines of code in software.
The OED describes the word as “computing slang” originating in the late 1950s but with an unknown origin. However I’ve always known the word for the first of the two meanings – as in the detritus which accumulates on a fan grille or dust bunnies.