Hastings' Dictionary of the Bible (1898)
STONE, WHITE, is supposed by many to be an allusion to the practice of some ancient nations of passing judgment on an accused person. Rev 2:17. Those in favor of acquitting him cast a white ball into an urn, and those who adjudged him guilty cast in a black ball; and if the number of the former exceeded that of the latter, the prisoner was discharged. Others think reference is made to the white stones which were given to conquerors in the
Olympian games with their names written upon them, and the value of the prize they won. So the new name mentioned in Isa 62:2 may denote the adoption of the individual into the family of God, by which he is admitted to privileges and blessings known only to him who possesses them. Archbishop Trench brings out what is probably the best interpretation. He repudiates the idea that this symbol was borrowed from heathen antiquity, and maintains it was
a diamond, the Urim and Thummim.