avoirdupois
Concise Oxford English Dictionary © 2008 Oxford University Press:
avoirdupois /ˌavwɑːdjʊˈpwɑː, ˌavədəˈpɔɪz/
▶noun a system of weights based on a pound of 16 ounces or 7,000 grains. Compare with troy.
– origin ME: from OFr. aveir de peis ‘goods of weight’, from aveir ‘to have’ (from L. habere) + peis (see poise1).
'avoirdupois' also found in these Oxford entries:

