Ghost Word
Ghost words appear in dictionary but aren't really used by anyone. Some of them result from straight up typos and mistakes. Dictionaries are obviously our all-powerful, linguistic overlords and thus "once authoritatively published, a ghost word commonly becomes widely copied and takes a long time to be erased from usage (e.g. "morse...); sometimes such a word even comes into permanent usage (e.g. "scapegoat"...)"
In one particularly hilarious incident "It turned out that "kimes" was a misprint for "knives", but the word gained currency for some time"
(Just some ye olde kime throwing...Pic from: www.juggling.org )
Also check out the wikionary page for abacot, a word that resulted from a Chinese whispers-esque string of misspellings of 'bycoket'...