This section is from the "A Complete Dictionary of Dry Goods" book, by George S. Cole. Also available from Amazon: A complete dictionary of dry goods and history of silk, cotton, linen, wool and other fibrous substances,: Including a full explanation of the modern processes ... together with various useful tables.
Foolscap. A writing paper, usually folded, varying in size from 12x15 to 12 1/2 x l6 inches; so called from its former watermark, the outline of a fool's head and cap, for which other devices are now substituted. The design originated with the English Rump Parliament, under Cromwell, who out of contempt for King Charles, ordered that the royal arms in the watermark of the paper should be removed, and a fool's cap and bells substituted. [See Paper]