exchequer (n.)

c. 1300, from Anglo-French escheker "a chessboard," from Old French eschequier, from Medieval Latin scaccarium "chess board" (see check (n.1); also see checker (n.2)). Government financial sense began under the Norman kings of England and refers to a cloth divided in squares that covered a table on which accounts of revenue were reckoned with counters, and which apparently reminded people of a chess board. Respelled with an -x- based on the mistaken belief that it originally was a Latin ex- word.