When researching this for the game, I found this very detailed explanation:
Checkmate: Chess was already an ancient game when the Persians introduced it to the Arabs. The Arabs retained the Persian word shah for king, the most important piece in the game, and when the shah (pronounce shag by Arabs) was maneuvered into a helpless position, ending play, they exclaimed shah mat, '(your) king is dead.' Soon after the Arabs introduced chess into Spain in the 8th century this expression became xague mate, from which derived the French eschec mate and finally the English checkmate.
Response last updated by Terry on Sep 18 2016.
Feb 23 2002, 6:04 AM