Someone seems to have made the tag 'grammer' (kind of ironic that it's misspelled) which is surely a misspelling of the (intended) tag 'grammar'. As of this writing there were 4 posts using this tag but I have proposed edits changing them all over to the 'grammar' tag. Can we get this tag deleted as it surely serves no purpose? We should also devise a way to prevent small mistakes like this in the future (though reputation privileges for tag creation would probably be an easy solution, but not for the private beta).
People make mistakes and I have seen many synonym or useless tags created on English Language and Usage. There is no way to prevent users from creating tags. As long as a user has one reputation point, they can creat tags now.
There are mechanisms to deal with this issue and I don't think it has a top priority when this site is under 'private beta' status.
According to the folloiwng Meta Stack Exahnge question, What are tag synonyms and merged tags? How do they work?
How can I delete/reverse/undo bad tag synonyms?
Only moderators can correct a bad synonym. Therefore the only recourse is to post a question on your meta site explaining the problem with the synonym relationship. Use the tags described as above. Give the community a few days to show support or make alternate proposals. Once the discussion has settled, a moderator will perform what correction is he or she deems necessary given the discussion.
Until we have moderators who can correct a bad tag, I think we need to rely on editing the question as you did.
Another related questions:
Tags not associated with any question are automatically destroyed at 03:00 UTC every day.