The tag untagged is applied to questions which either have all their tags burninated, or to questions migrated from other sites (when tags from the origin site do not match any tags here).
According to formal advice given by the SE team, this tag can be created at any time and should be edited out on any question that contains it ASAP, so that they are properly categorized (otherwise they could just languish as noise).
This meta question is to serve as a formal tag cleanup request for the untagged tag and should indefinitely exist without a status-completed tag even if the untagged tag is cleared, because it can be recreated at any time.
Why am I asking this request? Because then it will show in the list of tags that need cleaning, because many users use this to bring up a full list of tags that need cleaning. I should also mention that in the old monthly tag cleanups, we also had an explicit warning against this tag.
untaggedto be the last resort tag available on any site if I can't think up any related tags and the system won't allow me to post the question with zero tags. This allows editors to help me to tag the question correctly. Better to explicitly mark the questionuntaggedthan to mark it with random tag just to got though the barrier.