Source : Webster's Revised Unabridged Dictionary (1913)

Whipcord \Whip"cord`\, n.
   A kind of hard-twisted or braided cord, sometimes used for
   making whiplashes.

Source : WordNet®

whipcord
     n 1: closely twisted hard cord used for the lashes of whips
     2: a strong worsted or cotton fabric with a diagonal rib