avoirdupois

When "avoirdupois" first appeared in English in the 15th century, it carried a meaning of "goods sold by weight," which is also the meaning of its Middle English predecessor, "avoir de pois." That term derives from an Anglo-French phrase meaning "goods of weight." Today, "avoirdupois" most commonly refers to the system of weight measurement used for general merchandise, in which the pound is equal to 16 ounces, the ounce 16 drams, and the dram 27.344 grains. (Some other weight systems are apothecaries' weight, used to measure pharmaceutical items, and troy weight, used for precious metals.) It was Shakespeare, in his play Henry IV (1597), who first used "avoirdupois" to mean "heaviness."