The Collaborative International Dictionary of English v.0.48:

Sith \Sith\, prep., adv., & conj. [See Since.]
   Since; afterwards; seeing that. [Obs.]
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         We need not fear them, sith Christ is with us.
                                                  --Latimer.
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         Sith thou art rightful judge.            --Chaucer.
   [1913 Webster] Sith

The Collaborative International Dictionary of English v.0.48:

Sith \Sith\, Sithe \Sithe\, n. [AS. ??? a path, way, time,
   occasion.]
   Time. [Obs.] --Chaucer.
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         And humbly thanked him a thousand sithes. --Spenser.
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