The Collaborative International Dictionary of English v.0.48:

Whereto \Where*to"\, adv.
   [1913 Webster]
   1. To which; -- used relatively. "Whereto we have already
      attained." --Phil. iii. 16.
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            Whereto all bonds do tie me day by day. --Shak.
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   2. To what; to what end; -- used interrogatively.
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