Source : Webster's Revised Unabridged Dictionary (1913)

Whereto \Where*to"\, adv.
   1. To which; -- used relatively. ``Whereto we have already
      attained.'' --Phil. iii. 16.

            Whereto all bonds do tie me day by day. --Shak.

   2. To what; to what end; -- used interrogatively.

Source : WordNet®

whereto
     adv 1: to or unto which [syn: {whereunto}]
     2: to which; "the species whereto this name might be better
        applied"
     3: to what place, purpose, or end