1911 Encyclopædia Britannica/Shah
SHAH, the title of the kings of Persia, the full title being padshah, i.e. “lord king,” Pers. pati, lord, and shah, king (see Padishah, the Turkish form of the word). The word shah is a much shortened form of the O. Pers. khsayathiya, probably formed from khsayathi, might, power, khsi, to rule. The Sanskrit kshatrani, dominion, is allied, cf. also “satrap.” From the Pers. shāh māt, the king is dead, is ultimately derived, through the Arab. pronunciation shāg, “check-mate,” then “check,” “chess,” “exchequer,” &c.