The Collaborative International Dictionary of English v.0.48:

Supple-jack \Sup"ple-jack`\, n. (Bot.)
   (a) A climbing shrub (Berchemia volubilus) of the Southern
       United States, having a tough and pliable stem.
   (b) A somewhat similar tropical American plant (Paullinia
       Curassavica); also, a walking stick made from its stem.
       [1913 Webster]

             He was in form and spirit like a supple-jack, . . .
             yielding, but tough; though he bent, he never
             broke.                               --W. Irving.
       [1913 Webster]

   Note: This name is given to various plants of similar habit
         in different British colonies.
         [1913 Webster]