The Collaborative International Dictionary of English v.0.48:

Dewclaw \Dew"claw`\, n.
   In any animal, esp. of the Herbivora, a rudimentary claw or
   small hoof not reaching the ground.
   [1913 Webster]

         Some cut off the dewclaws [of greyhounds]. --J. H.
                                                  Walsh.
   [1913 Webster]