Thread:Project:Support desk/Tooltip on sidebar items?

Hi, I have been unable to find any documentation on how to change the mouse-over text (or, indeed, add any) for the items in the sidebar. Can someone tell me where in the database to look, or (better yet) point me to a place where the procedure is explained?

The version-info for the wiki is:

MediaWiki	1.17.0 PHP	5.2.17 (cgi) MySQL	5.1.56-community-log