Tolkien's Use of Thongs

Apparently I may be mistaken in how Tolkien used thongs ... I mean in his writing. In some of his works he uses the term thongs as leather straps used to bind or as the thongs of a whip. So I guess that unfortunate Dwarf might not have gotten shoes after all. I guess I just didn't see the purpose of tying him up before locking him in a cell...