Poking around on the site, I noticed that the untagged tag has 28 questions in it.
If you can spare a few minutes, please try to grab a few questions where you recognize the subject from the list and add appropriate tag(s); this'll help folks find them more easily in the future. If a tag needs to be created for one of these questions and you don't have the necessary privilege, just leave a note for me here and I'll add it.
Most of these are probably due to single-use tags that were deleted automatically after 6 months; the system will remove tags that aren't used more than once unless someone has written a tag wiki for it. I see that several people here have been adding such wikis for more obscure tags (for example, closed-transfer) - thanks, this'll save having to re-add the tag in the future!