The Collaborative International Dictionary of English v.0.48:

Caddie \Cad"die\, n. [Written also caddy, cadie, cady, and
   cawdy.] [See Cadet.]
   1. A cadet. [Obs. Scot.]
      [Webster 1913 Suppl.]

   2. A lad; young fellow. [Scot.] --Burns.
      [Webster 1913 Suppl.]

   3. One who does errands or other odd jobs. [Scot.]
      [Webster 1913 Suppl.]

   4. An attendant who carries a golf player's clubs, tees his
      ball, etc.
      [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Cadie \Cad"ie\, Caddie \Cad"die\, n.
   A Scotch errand boy, porter, or messenger. [Written also
   cady.]
   [1913 Webster]

         Every Scotchman, from the peer to the cadie.
                                                  --Macaulay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

caddie
    n 1: an attendant who carries the golf clubs for a player [syn:
         caddie, golf caddie]
    v 1: act as a caddie and carry clubs for a player [syn:
         caddie, caddy]

Moby Thesaurus II by Grady Ward, 1.0:

64 Moby Thesaurus words for "caddie":
   Aquarius, Ganymede, Hebe, airline hostess, airline stewardess,
   attendant, batman, bearer, bellboy, bellhop, bellman, bheesty,
   bootblack, boots, busboy, cabin boy, cargo handler, carrier,
   carrier pigeon, carter, chore boy, common carrier, conveyer,
   coolie, copyboy, cupbearer, drayman, errand boy, errand girl,
   express, expressman, footboy, freighter, gofer, gun bearer, hauler,
   homing pigeon, hostess, letter carrier, litter-bearer, office boy,
   office girl, orderly, page, porter, redcap, shield-bearer, skycap,
   squire, stevedore, steward, stewardess, stretcher-bearer, tender,
   the Water Bearer, trainbearer, transporter, truck driver, trucker,
   usher, wagoner, water boy, water carrier, yeoman