Thyself

[Sarah]

An emphasized form of the personal pronoun of the secondperson; -- used as a subject commonly with thou; as, thou thyselfshalt go; that is, thou shalt go, and no other. It is sometimes used,especially in the predicate, without thou, and in the nominative aswell as in the objective case.Thyself shalt see the act. Shak.Ere I do thee, thou to thyself wast cruel. Milton.

[Tracie Lynn]

yourself: the reflexive form or strong form of thou , used when speaking to one person