The Collaborative International Dictionary of English v.0.48:

Johnny \John"ny\, n.; pl. Johnnies.
   1. A familiar diminutive of John.
      [1913 Webster]

   2. (Zool.) A sculpin. [Local cant]
      [1913 Webster]

   Johny Crapaud, a jocose designation of a Frenchman, or of
      the French people, collectively.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Johnny
    n 1: `Johnny' was applied as a nickname for Confederate soldiers
         by the Federal soldiers in the American Civil War;
         `greyback' derived from their grey Confederate uniforms
         [syn: Rebel, Reb, Johnny Reb, Johnny, greyback]

Moby Thesaurus II by Grady Ward, 1.0:

83 Moby Thesaurus words for "johnny":
   Adamite, WC, backhouse, basement, bastard, bathroom, bedpan, being,
   bird, body, bugger, can, cat, chamber, chamber pot, chap,
   character, chemical closet, chemical toilet, closet,
   comfort station, commode, convenience, crapper, creature, customer,
   duck, earth closet, earthling, feller, fellow, groundling, guy,
   hand, head, homo, human, human being, individual, jasper, jerry,
   john, johnny house, joker, jordan, lad, latrine, lavatory, life,
   living soul, loo, man, mortal, necessary, nose, one, outhouse,
   party, person, personage, personality, piss pot, potty,
   potty-chair, powder room, privy, rest room, single, somebody,
   someone, soul, stool, stud, tellurian, terran, throne, thunder mug,
   toilet, toilet room, urinal, washroom, water closet, worldling