Source : Webster's Revised Unabridged Dictionary (1913)

Cowherd \Cow"herd`\ (-h?rd`), n. [AS. c[=u]hyrde; c[=u] cow +
   hyrde a herder.]
   One whose occupation is to tend cows.

Source : WordNet®

cowherd
     n : a hired hand who tends cattle and performs other duties on
         horseback [syn: {cowboy}, {cowpuncher}, {puncher}, {cowman},
          {cattleman}, {cowpoke}, {cowhand}]