The Collaborative International Dictionary of English v.0.48:

Thong \Thong\, n. [OE. thong, [thorn]wong, thwang, AS.
   [thorn]wang; akin to Icel. [thorn]vengr a thong, latchet.
   [root]57. Cf. Twinge.]
   A strap of leather; especially, one used for fastening
   anything.
   [1913 Webster]

         And nails for loosened spears, and thongs for shields,
         provide.                                 --Dryden.
   [1913 Webster]

   Thong seal (Zool.), the bearded seal. See the Note under
      Seal.
      [1913 Webster]

WordNet (r) 3.0 (2006):

thong
    n 1: leather strip that forms the flexible part of a whip [syn:
         lash, thong]
    2: underpants resembling a G-string; worn by women especially
       under very tight pants; "she wore thongs in her quest for the
       callipygian ideal"
    3: a thin strip of leather; often used to lash things together
    4: minimal clothing worn by stripteasers; a narrow strip of
       fabric that covers the pubic area, passes between the thighs,
       and is supported by a waistband [syn: G-string, thong]
    5: a backless sandal held to the foot by a thong between the big
       toe and the second toe [syn: flip-flop, thong]

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "thong":
   belt, blacksnake, braid, brail, bullwhack, bullwhip, cable, cat,
   cord, cowhide, crop, flagellum, horsewhip, knout, kurbash, lash,
   ligament, ligation, ligature, line, quirt, rawhide, razor strap,
   rope, scourge, sjambok, spun yarn, strap, string, tendon, twine,
   twist, whip, whiplash, wire, yarn