The Collaborative International Dictionary of English v.0.48:

Corroborate \Cor*rob"o*rate\ (k?r-r?b"?-r?t), v. t. [imp. & p.
   p. Corroborated (-r?`t?d); p. pr. & vb. n. Corroborating
   (-r?`t?ng). ] [L. corroboratus, p. p. of corroborare to
   corroborate; cor- + roborare to strengthen, robur strength.
   See Robust.]
   1. To make strong, or to give additional strength to; to
      strengthen. [Obs.]
      [1913 Webster]

            As any limb well and duly exercised, grows stronger,
            the nerves of the body are corroborated thereby.
                                                  --I. Watts.
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   2. To make more certain; to confirm; to establish.
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            The concurrence of all corroborates the same truth.
                                                  --I. Taylor.
      [1913 Webster]