1. a system of weights based on a pound of 16 ounces or 7,000 grains, widely used in English-speaking countries: "avoirdupois weights"
▪ weight; heaviness:"she was putting on the avoirdupois like nobody's business"
Word OriginMiddle English (denoting merchandise sold by weight): from Old French aveir de peis ‘goods of weight’, from aveir ‘to have’ (infinitive used as a noun, from Latin habere) + peis ‘weight’ (see poise1).
Avoirdupois is a measurement system of weights that uses pounds and ounces as units. It was first commonly used in the 13th century AD and was updated in 1959. Wikipedia