plural of die (n.), early 14c., des, dys, plural of dy, altered 14c. to dyse, dyce, and 15c. to dice. "As in pence, the plural s retains its original breath sound, probably because these words were not felt as ordinary plurals, but as collective words" [OED]. Sometimes used as singular 1400-1700. Dice-box "box from which dice are thrown in gaming" is from 1550s.