An Etymological Dictionary of Astronomy and Astrophysics

1. Something that one is expected or required to do by moral or legal → obligation.
   

2. The binding or obligatory force of something that is morally or legally right; moral or legal obligation.
   

3. An → action or → task required by a person’s position or occupation; → function (Dictionary.com).

Etymology (EN): M.E. du(e)te, from Anglo-Fr. duete, from O.Fr. deu “due, owed; proper, just,” from V.L. *debutus, from L. debitus, p.p. of debere “to owe.”

Etymology (PE): Harg, from Mid.Pers. harg, halg “duty, tribute; work, effort;” akin to Mod.Pers. gahulidan “to exchange, barter,” → exchange; cf. Wakhi (y)ark “work, matter, business”, Yaghnobi ark “work, matter, business,” Yighda hor, Munji hôr(g) “work;” Proto-Ir. *harH- “to pay tribute; to barter, trade, exchange;” cognate with Gk. elein “to take (by force),” elor “loot, looty, catch;” E. to sell (Cheung 2006).