The Collaborative International Dictionary of English v.0.48:

Callid \Cal"lid\, a. [L. callidus, fr. callere to be
   thick-skinned, to be hardened, to be practiced, fr. callum,
   callus, callous skin, callosity, callousness.]
   Characterized by cunning or shrewdness; crafty. [R.]
   [1913 Webster]