late 14c., duete, "obligatory service, that which ought to be done," also "the force of that which is morally right," from Anglo-French duete, from Old French deu "due, owed," hence "proper, just" (on the notion of "that which one is bound by natural, moral, or legal obligation to do or perform"); from Vulgar Latin *debutus, from Latin debitus, past participle of debere "to owe," originally, "keep something away from someone," from de- "away" (see de-) + habere "to have" (from PIE root *ghabh- "to give or receive"). Related: Duties.
Military sense of "a requisite service" is by 1580s. The sense of "tax or fee on imports, exports, etc." is from late 14c.; hence duty-free (adv.) "free from tax or duty" (1680s), and, as a noun, "duty-free article" (1958), "duty-free shop" (by 1980).
also *ghebh-, Proto-Indo-European root meaning "to give or receive." The basic sense of the root probably is "to hold," which can be either in offering or in taking.
It forms all or part of: able; avoirdupois; binnacle; cohabit; cohabitation; debenture; debit; debt; dishabille; due; duty; endeavor; exhibit; exhibition; forgive; gavel; gift; give; habeas corpus; habiliment; habit; habitable; habitant; habitat; habitation; habitual; habituate; habituation; habitude; habitue; inhabit; inhibit; inhibition; malady; prebend; prohibit; prohibition; provender.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit gabhasti- "hand, forearm;" Latin habere "to have, hold, possess," habitus "condition, demeanor, appearance, dress;" Old Irish gaibim "I take, hold, I have," gabal "act of taking;" Lithuanian gabana "armful," gabenti "to remove;" Gothic gabei "riches;" Old English giefan, Old Norse gefa "to give."
"one who fails to perform some duty or obligation," 1650s, agent noun from default (v.).
early 15c., "pains taken to attain an object," literally "in duty," from phrase put (oneself) in dever "make it one's duty" (a partial translation of Old French mettre en deveir "put in duty"), from Old French dever "duty," from Latin debere "to owe," originally, "keep something away from someone," from de- "away" (see de-) + habere "to have" (from PIE root *ghabh- "to give or receive"). One's endeavors meaning one's "utmost effort" is from late 15c.