thyself definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
Archaic thou: a var. of yourself
Origin: Middle English thi self, superseding earlier the self, literally , thee self ; from Old English the self; in Middle English self, origin, originally adjective , was regarded as noun
thyself definition by American Heritage Dictionary
Yourself. Used as the reflexive or emphatic form of thee or thou.