How do I find tag misspellings that are only used once?

So I just created this question on the Answers board (shameless promotion), and when typing in the "maintenance" tag, there were two tags already in existence that were misspelled:

• Maintanence
• Maintenence

(if I remember correctly)

Anyways, I went to search for them under the "Tags" tab and found that they weren't listed there! Along with the new-to-me assertion that tags are only shown if they're used more than once.

So how do I track down these stray misspellings and fix them?