Boo! It's a ghost . . . word
Have you ever heard of the term ghost word? It doesn't have a direct connection to Halloween . . . although that's a good guess. No, a ghost word is a word that "has come into existence by error rather than by normal linguistic transmission, as through the mistaken reading of a manuscript, a scribal error, or a misprint." Walter William Skeat coined this term back in 1886.
Someone somewhere tossed out a word in error, but it didn't really look like a typo, and it rolled by many a copyeditor without anyone flagging it. Before you know it, the ghost word becomes a word! Maybe it doesn't get a lot of use, but it's still out there floating in the ether, waiting for its next opportunity to surface. Join us as we walk through these linguistic anomalies.