Debian has a naming convention which names distributions according to its reliability rather than its version. It is a tradition among the Debian community to name the distribution with the name of a Great Hacker who has contributed to the Debian project. So Woody, Sarge, Sid, Potato ... these all are surnames of the great programmers who have worked for the debian project. Currently Debian distributions are named in the following order.
Debian 'Un Named' -> Experimental release <latest version>
Debian 'Sid' -> Unstable release
Debian 'Sarge' -> Testing release
Debian 'Woody' -> Stable release <most rock solid>
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Debian 'potato' -> very old release