Source : Webster's Revised Unabridged Dictionary (1913)

Withers \With"ers\, n. pl. [Properly, the parts which resist the
   pull or strain in drawing a load; fr. OE. wither resistance,
   AS. wi[eth]re, fr. wi[eth]er against; akin to G. widerrist
   withers. See {With}, prep.]
   The ridge between the shoulder bones of a horse, at the base
   of the neck. See Illust. of {Horse}.

         Let the galled jade wince; our withers are unwrung.
                                                  --Shak.

Source : WordNet®

withers
     n 1: sensibility to trouble (as in the phrase `wring one's
          withers'); "the lawsuit was wringing his withers"; "our
          withers are unwrung"--Shakespeare
     2: the highest part of the back at the base of the neck of
        various animals especially draft animals