The Collaborative International Dictionary of English v.0.48:

Unto \Un"to\, prep. [OE. unto; un- (only in unto, until) unto,
   as far as + to to; this un- is akin to AS. ?? until, OFries.
   und OS. und until, conj. (cf. OS. unt? unto, OHG. unzi),
   Goth. und unto, until. See To, and cf. Until.]
   [1913 Webster]
   1. To; -- now used only in antiquated, formal, or scriptural
      style. See To.
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   2. Until; till. [Obs.] "He shall abide it unto the death of
      the priest." --Num. xxxv. 25.
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The Collaborative International Dictionary of English v.0.48:

Unto \Un"to\, conj.
   Until; till. [Obs.] "Unto this year be gone." --Chaucer.
   [1913 Webster]