The unusual flowering time has to do with witchcraft--this is the superficial way to explain why witch-hazel is called so. There is, however, a more sophisticated treatment: "witch" comes from an Old-English 'wych' that further leads to 'wice' with the meaning "bend" or "flexible". This Indo-European root has made it in many languages. The Russian for "branch"--"vetv" and "branchlet"--"vetochka" originate from the same source. Even closer is a dialect word used in the Urals with the same meaning that sounds like "vitchka"!