deadline (n.) Look up deadline at Dictionary.com
"time limit," 1920, American English newspaper jargon, from dead (adj.) + line (n.). Perhaps influenced by earlier use (1864) to mean the "do-not-cross" line in Civil War prisons, which figured in the Wirz trial.
And he, the said Wirz, still wickedly pursuing his evil purpose, did establish and cause to be designated within the prison enclosure containing said prisoners a "dead line," being a line around the inner face of the stockade or wall enclosing said prison and about twenty feet distant from and within said stockade; and so established said dead line, which was in many places an imaginary line, in many other places marked by insecure and shifting strips of [boards nailed] upon the tops of small and insecure stakes or posts, he, the said Wirz, instructed the prison guard stationed around the top of said stockade to fire upon and kill any of the prisoners aforesaid who might touch, fall upon, pass over or under across the said "dead line" .... ["Trial of Henry Wirz," Report of the Secretary of War, Oct. 31, 1865]
deadlock (n.) Look up deadlock at Dictionary.com
"complete standstill," from dead (adj.), in its emphatic use, + lock (n.). First attested 1779 in Sheridan's play "The Critic."
deadly (adj.) Look up deadly at Dictionary.com
Old English deadlic "mortal, subject to death," also "causing death;" see dead + -ly (1). Meaning "having the capacity to kill" is from late 14c. (Old English words for this included deaðbærlic, deaðberende).
deadpan Look up deadpan at Dictionary.com
1928, from dead (adj.) + pan (n.) in slang sense of "face."
deadweight (n.) Look up deadweight at Dictionary.com
1650s, "weight of an inert body," from dead (adj.) + weight (n.).
deadwood (n.) Look up deadwood at Dictionary.com
1887 in figurative sense of "useless person or thing," originally American English, from dead (adj.) + wood (n.). Dead wood in a forest is useful as firewood; perhaps the reference here is to the dried up parts of plants grown for commercial production of flowers or fruit.
deaf (adj.) Look up deaf at Dictionary.com
Old English deaf "deaf," also "empty, barren," specialized from Proto-Germanic *daubaz (cognates: Old Saxon dof, Old Norse daufr, Old Frisian daf, Dutch doof "deaf," German taub, Gothic daufs "deaf, insensate"), from PIE dheubh-, which was used to form words meaning "confusion, stupefaction, dizziness" (cognates: Greek typhlos "blind," typhein "to make smoke;" Old English dumb "unable to speak;" Old High German tumb).

The word was pronounced to rhyme with reef until 18c. Deaf-mute is from 1837, after French sourd-muet. Deaf-mutes were sought after in 18c.-19c. Britain as fortune-tellers. Deaf as an adder (Old English) is from Psalms lviii:5.
deafen (v.) Look up deafen at Dictionary.com
1590s, "to make deaf," from deaf + -en (1). The earlier verb was simply deaf (mid-15c.). For "to become deaf, to grow deaf," Old English had adeafian (intransitive), which survived into Middle English as deave but then took on a transitive sense from mid-14c. and sank from use except in dialects (where it mostly has transitive and figurative senses), leaving English without an intransitive verb here.
deafening (adj.) Look up deafening at Dictionary.com
"very loud," 1590s, from present participle of deafen (q.v.). Deafening silence is attested by 1830.
deafness (n.) Look up deafness at Dictionary.com
late 14c., from deaf + -ness.
deal (n.1) Look up deal at Dictionary.com
from Old English dæl "part, share, quantity, amount," from Proto-Germanic *dailaz (cognates: Old Norse deild, Old Frisian del, Dutch deel, Old High German and German teil, Gothic dails "part, share"), from PIE *dail- "to divide" (cognates: Old Church Slavonic delu "part," Lithuanian dalis).

Business sense of "transaction, bargain" is 1837, originally slang. Meaning "an amount" is from 1560s. New Deal is from F.D. Roosevelt speech of July 1932. Big deal is 1928; ironic use first recorded 1951 in "Catcher in the Rye." Deal breaker is attested by 1975.
deal (n.2) Look up deal at Dictionary.com
"plank or board of pine," c.1400, from Low German (compare Middle Low German dele), from Proto-Germanic *theljon, from PIE root *tel- "ground, floor." An Old English derivative was þelu "hewn wood, board, flooring."
deal (v.) Look up deal at Dictionary.com
Old English dælan "to divide, distribute, separate, share, bestow, dispense," from the source of deal (n.). Meaning "to distribute cards before a game" is from 1520s. To deal with "handle" is attested from mid-15c. Related: Dealt; dealing.
dealer (n.) Look up dealer at Dictionary.com
Old English dælere "divider, distributor; agent, negotiator," agent noun from deal (v.). Meaning "player who passes out the cards in a game" is from c.1600; meaning "one who deals in merchandise" is from 1610s. Illegal drug sense is recorded by 1920.
dealership (n.) Look up dealership at Dictionary.com
1916, from dealer + -ship.
dealt Look up dealt at Dictionary.com
past tense and past participle of deal (v.).
deamination (n.) Look up deamination at Dictionary.com
1912, from de- + amine + -ation.
dean (n.) Look up dean at Dictionary.com
early 14c., from Old French deien (12c., Modern French doyen), from Late Latin decanus "head of a group of 10 monks in a monastery," from earlier secular meaning "commander of 10 soldiers" (which was extended to civil administrators in the late empire), from Greek dekanos, from deka "ten" (see ten). Replaced Old English teoðingealdor. College sense is from 1570s (in Latin from late 13c.).
dear (adj.) Look up dear at Dictionary.com
Old English deore "precious, valuable, costly, loved, beloved," from Proto-Germanic *deurjaz (cognates: Old Saxon diuri, Old Norse dyrr, Old Frisian diore, Middle Dutch dure, Dutch duur, Old High German tiuri, German teuer), ultimate origin unknown. Used interjectorily since 1690s. As a polite introductory word to letters, it is attested from mid-15c. As a noun, from late 14c., perhaps short for dear one, etc.
dearborn (n.) Look up dearborn at Dictionary.com
"light four-wheeled wagon," 1821, American English, supposedly from the name of the inventor, by tradition said to be Gen. Henry Dearborn (1751-1829).
dearly (adv.) Look up dearly at Dictionary.com
Old English deorlice (see dear).
dearth (n.) Look up dearth at Dictionary.com
mid-13c., derthe "scarcity" (originally used of famines, when food was costly because scarce; extended to other situations of scarcity from early 14c.), abstract noun formed from root of Old English deore "precious, costly" (see dear) + abstract noun suffix -th (2). Common Germanic formation, though not always with the same sense (cognates: Old Saxon diurtha "splendor, glory, love," Middle Dutch dierte, Dutch duurte, Old High German tiurida "glory").
deary (n.) Look up deary at Dictionary.com
also dearie, diminutive of dear with a notion of "dear one."
deasil (adj.) Look up deasil at Dictionary.com
"rightwise, turned toward the right; motion according to the apparent course of the sun," 1771, from Gaelic deiseil, deiseal (adjective and adverb) "toward the south," taken in sense of "toward the right," from deas "right, right-hand; south," cognate with Irish deas, Old Irish dess, des, Welsh dehau, and ultimately with Latin dexter (see dexterity). The second element of the Gaelic word is not explained (one old guess, in the Century Dictionary (1902), is a proposed *iul "direction, guidance").
death (n.) Look up death at Dictionary.com
Old English deað "death, dying, cause of death," in plura, "ghosts," from Proto-Germanic *dauthaz (cognates: Old Saxon doth, Old Frisian dath, Dutch dood, Old High German tod, German Tod, Old Norse dauði, Danish død, Swedish död, Gothic dauþas "death"), from verbal stem *dheu- (3) "to die" (see die (v.)) + *-thuz suffix indicating "act, process, condition."
I would not that death should take me asleep. I would not have him meerly seise me, and onely declare me to be dead, but win me, and overcome me. When I must shipwrack, I would do it in a sea, where mine impotencie might have some excuse; not in a sullen weedy lake, where I could not have so much as exercise for my swimming. [John Donne, letter to Sir Henry Goodere, Sept. 1608]
Death's-head, a symbol of mortality, is from 1590s. Death row first recorded 1940s. Death knell is attested from 1814; death penalty from 1875; death rate from 1859. Slang be death on "be very good at" is from 1839. Death wish first recorded 1896. The death-watch beetle (1660s) inhabits houses, makes a ticking noise like a watch, and was superstitiously supposed to portend death.
FEW ears have escaped the noise of the death-watch, that is, the little clickling sound heard often in many rooms, somewhat resembling that of a watch; and this is conceived to be of an evil omen or prediction of some person's death: wherein notwithstanding there is nothing of rational presage or just cause of terror unto melancholy and meticulous heads. For this noise is made by a little sheathwinged grey insect, found often in wainscot benches and wood-work in the summer. [Browne, "Vulgar Errors"]
death camp (n.) Look up death camp at Dictionary.com
1944, in reference to the Nazis, probably translating German Todeslager; they also were known as extermination camps (German Vernichtungslager); historians usually count six of them: Auschwitz-Birkenau, Chełmno, Bełżec, Majdanek, Sobibór, Treblinka.
deathbed (n.) Look up deathbed at Dictionary.com
Old English, "the grave," from death (n.) + bed (n.). Meaning "bed on which someone dies" is from c.1300.
deathless (adj.) Look up deathless at Dictionary.com
1580s, from death + -less. Related: Deathlessly; deathlessness.
deathly (adj.) Look up deathly at Dictionary.com
Old English deaþlic "mortal" (see death). Meaning "deadly" is from late 12c.; that of "death-like" is from 1560s.
deb (n.) Look up deb at Dictionary.com
slang shortening of debutante, by 1920.
debacle (n.) Look up debacle at Dictionary.com
"disaster," 1848, from French débâcle "downfall, collapse, disaster" (17c.), a figurative use, literally "breaking up (of ice on a river)," extended to the violent flood that follows when the river ice melts in spring; from débâcler "to free," from Middle French desbacler "to unbar," from des- "off" + bacler "to bar," from Vulgar Latin *bacculare, from Latin baculum "stick" (see bacillus). Sense of "disaster" was present in French before English borrowed the word.
debar (v.) Look up debar at Dictionary.com
early 15c., "to shut out, exclude," from French débarrer, from Old French desbarer (12c., which, however, meant only "to unbar, unbolt," the meaning turned around in French as the de- was felt in a different sense), from des- (see dis-) + barrer "to bar" (see bar (n.1)). Related: Debarment; debarred.
debark (v.) Look up debark at Dictionary.com
1650s, from French débarquer (16c.), from de- (Old French des-; see dis-) + barque "bark" (see bark (n.2)).
debase (v.) Look up debase at Dictionary.com
1560s, from de- "down" + base (adj.) "low," on analogy of abase (or, alternatively, from obsolete verb base "to abuse").
debatable (adj.) Look up debatable at Dictionary.com
1530s (late 15c. in Anglo-Latin), from Old French debatable (Modern French débattable), from debatre (see debate (v.)). Earliest references were to lands claimed by two nations; general sense is from 1580s.
debate (v.) Look up debate at Dictionary.com
late 14c., "to quarrel, dispute," also "discuss, deliberate upon the pros and cons of," from Old French debatre (13c., Modern French débattre), originally "to fight," from de- "down, completely" (see de-) + batre "to beat" (see battery). Related: Debated; debating.
debate (n.) Look up debate at Dictionary.com
early 14c., "a quarrel, dispute, disagreement," from Old French debat; see debate (v.). Sense of "a formal dispute, a debating contest" is perhaps from early 15c.
debauch (v.) Look up debauch at Dictionary.com
1590s, from Middle French débaucher "entice from work or duty," from Old French desbaucher "to lead astray," supposedly literally "to trim (wood) to make a beam" (from bauch "beam," from Frankish balk or some other Germanic source akin to English balk (n.)). A sense of "shaving" something away, perhaps, but the root is also said to be a word meaning "workshop," which gets toward the notion of "to lure someone off the job;" either way the sense evolution is unclear.
debauchee (n.) Look up debauchee at Dictionary.com
1660s, from French débauché "debauched (person)," noun use of past participle of debaucher (see debauch).
Debauchee, n. One who has so earnestly pursued pleasure that he has had the misfortune to overtake it. [Ambrose Bierce, "Devil's Dictionary," 1911]
debauchery (n.) Look up debauchery at Dictionary.com
1640s, from debauch + -ery. With a variety of spellings in 17c., such as debaush-, deboich-, debosh-.
debenture (n.) Look up debenture at Dictionary.com
"written acknowledgment of a debt," early 15c., from Latin debentur "there are due" (said to have been the first word in formal certificates of indebtedness), passive present third person plural of debere "to owe" (see debt).
debilitate (v.) Look up debilitate at Dictionary.com
1530s, from Latin debilitatus, past participle of debilitare "to weaken," from debilis "weak" (see debility). Related: Debilitated; debilitating.
debilitation (n.) Look up debilitation at Dictionary.com
early 15c., from French débilitation (13c.), from Latin debilitationem (nominative debilitas) "a laming, crippling, weakening," noun of action from past participle stem of debilitare "to weaken" (see debilitate).
debility (n.) Look up debility at Dictionary.com
early 15c., from Middle French debilite (Modern French débilité) or directly from Latin debilitatem (nominative debilitas) "a laming, crippling, weakening," from debilis "lame, disabled, crippled," figuratively "weak, helpless," from de- "from, away" (see de-) + -bilis "strength," from PIE root *bel- (see Bolshevik).
debit (n.) Look up debit at Dictionary.com
mid-15c., from Middle French debet or directly from Latin debitum "thing owed, that which is owing," neuter past participle of debere "to owe" (see debt). As a verb from 1680s. Debit card is attested from 1975.
debonair (adj.) Look up debonair at Dictionary.com
c.1200, "mild, gentle, kind courteous," from Old French debonaire, from de bon' aire "of good race," originally used of hawks, hence, "thoroughbred" (opposite of French demalaire). Used in Middle English to mean "docile, courteous," it became obsolete and was revived with an altered sense of "pleasant, affable" (1680s).
Deborah Look up Deborah at Dictionary.com
fem. proper name, prophetess and judge in the Old Testament, Hebrew, literally "bee" (thus the name is the same as Melissa).
deboshed (adj.) Look up deboshed at Dictionary.com
1590s, anglicized spelling of French pronunciation of debauched "dissolute" (see debauch). Obsolete in England after mid-17c., retained in Scotland, and given a revival of sorts by Scott (1826), so that it turns up in 19c. literary works.
debridement (n.) Look up debridement at Dictionary.com
"removal of damaged tissue from a wound," 1839, from French débridement, literally "an unbridling," from dé- (see de-) + bride "bridle," from a Germanic source akin to Middle High German bridel (see bridle). Related: debride, debriding.
debrief (v.) Look up debrief at Dictionary.com
"obtain information (from someone) at the end of a mission," 1945, from de- + brief (v.). Related: Debriefed; debriefing.