Source : Webster's Revised Unabridged Dictionary (1913)

Agnus castus \Ag"nus cas"tus\ [Gr. ? a willowlike tree, used at
   a religious festival; confused with ? holy, chaste.] (Bot.)
   A species of {Vitex} ({V. agnus castus}); the chaste tree.
   --Loudon.

         And wreaths of agnus castus others bore. --Dryden.