From BiblePortal Wikipedia
Webster's Dictionary 
(pron.) An emphasized form of the personal pronoun of the second person; - used as a subject commonly with thou; as, thou thyself shalt go; that is, thou shalt go, and no other. It is sometimes used, especially in the predicate, without thou, and in the nominative as well as in the objective case.
King James Dictionary 
Thyself', pron. thy and self. A pronoun used after thou, to express distinction with emphasis. "Thou thyself shalt go " that is, thou shalt go and no other. It is sometimes used without thou, and in the nominative as well as objective case.
These goods thyself can on thyself bestow.