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.
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         And nails for loosened spears, and thongs for shields,
         provide.                                 --Dryden.
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   Thong seal (Zool.), the bearded seal. See the Note under
      Seal.
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