Smith, said he used 'interpreters' to translate the Book of Mormon from the metal plates. The 'interpreters' he described as a pair of stones, fastened to a breastplate joined in a form similar to that of a large pair of spectacles. Smith later referred to this object as the Urim and Thummim. In 1823, Smith said that the angel Moroni, who had told him about the golden plates, also told him about the Urim and Thummim, 'two stones in silver bows' fastened to a breastplate, and the angel intimated that they had been prepared by God to aid in the translation of the golden plates. Smith's mother, Lucy Mack Smith, described these Urim and Thummim as being like 'two smooth three-cornered diamonds'.
Thummim is widely considered to be derived from the consonantal root (t-m-m), meaning faultles, while scholars believe that the word Urim simply derives from the Hebrew term, 'Arrim', meaning curses, and thus that Urim and Thummim essentially means cursed and faultless, in reference to the deity's view of an accused - in other words that Urim and Thummim concern the question of innocent or guilty.