It's a feminine form of John.
This user-submitted entry seems legitimate:
http://www.behindthename.com/submit/view.php?name=jehanne
Google it and you'll see that it was probably the actual form of Joan of Arc's first name.
~~~~~Amanda~~~~~Midnight stands darkly on the road,
and burdened by stars, tumbles down.
You can't step beyond your fence
without trampling the universe.
-"The Steppe" Boris Pasternak