Source : Webster's Revised Unabridged Dictionary (1913)

Capapie \Cap`*a*pie"\, adv. [OF. (?) cap-a-pie, from head to
   foot, now de pied en cap from foot to head; L. per foot +
   caput head.]
   From head to foot; at all points. ``He was armed cap-a-pie.''
   --Prescott.