Source : Webster's Revised Unabridged Dictionary (1913)

Case knife \Case" knife`\
   1. A knife carried in a sheath or case. --Addison.

   2. A large table knife; -- so called from being formerly kept
      in a case.

Source : WordNet®

case knife
     n 1: a metal blade with a handle; used as cutlery
     2: a knife with a fixed blade that is carried in a sheath [syn:
         {sheath knife}]