E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Court of Exchequer. In the subdivision of the court in the reign of Edward I., the Exchequer acquired a separate and independent position. Its special duty was to order the revenues of the Crown and recover the kings debts. It was denominated Scaccarium, from scaccum (a chess-board), and was so called because a chequered cloth was laid on the table of the court. (Madox: History of the Exchequer.)
Foss, in his Lives of the Judges, gives a slightly different explanation. He says: All round the table was a standing ledge four fingers broad, covered with a cloth bought in the Easter Term, and this cloth was black rowed with strekes about a span, like a chess-board. On the spaces of this cloth counters were arranged, marked for checking computations.