The body of the instrument is very small, but it has a relatively long fingerboard in order to accommodate the player's hand.
An alternative musical use of the word kit is as an abbreviation for drum kit.
On Usenet, a kit is possibly from DEC Slang for a full software distribution, as opposed to a patch or upgrade. A source software distribution that has been packaged in such a way that it can (theoretically) be unpacked and installed according to a series of steps using only standard Unix tools, and entirely documented by some reasonable chain of references from the top-level README file. The more general term distribution may imply that special tools or more stringent conditions on the host environment are required.
The last part of this article (or an earlier version of it) contains material from FOLDOC, used with permission.