Online Etymology Dictionary

dignity (n.): early 13c., from Old French dignite "dignity, privilege, honor," from Latin dignitatem (nominative dignitas) "worthiness," from dignus "worth (n.), worthy, proper, fitting" from PIE *dek-no-, from root *dek- "to take, accept" (see decent).
digraph (n.): 1788, in linguistics, from Greek di- "twice" (see di- (1)) + -graph "something written," from Greek graphe "writing," from graphein "to write, express by written characters," earlier "to draw, represent by lines drawn" (see -graphy). In mathematics, from 1955, a contraction of directed graph.
digress (v.): 1520s, from Latin digressus, past participle of digredi "to go aside, depart" (see digression), or perhaps a back-formation from digression. Related: Digressed; digressing.
digression (n.): late 14c., from Latin digressionem (nominative digressio) "a going away, departing," noun of action from past participle stem of digredi "to deviate," from dis- "apart, aside" (see dis-) + gradi "to step, go" (see grade (n.)).
digs (n.): "lodgings," slang attested from 1893, from dig.
dike (n.): Old English dic "trench, ditch; an earthwork with a trench; moat," from Proto-Germanic *dik- (cf. Old Norse diki "ditch, fishpond," Old Frisian dik "mound, dam," Middle Dutch dijc "mound, dam, pool," Dutch dijk "dam," German Deich "embankment"), from PIE root *dheigw- "to pierce, fasten" (cf. Sanskrit dehi- "wall," Old Persian dida "wall, stronghold, fortress," Persian diz).

At first "an excavation," later (late 15c.) applied to the resulting earth mound; a sense development paralleled by cognate forms in many other languages. This is the northern variant of the word that in the south of England yielded ditch (n.).
diktat (n.): 1933, from German Diktat "dictate."
dilapidate (v.): 1560s, "to bring a building to ruin," from Latin dilapidatus, past participle of dilapidare "to squander, waste," originally "to throw stones, scatter like stones;" see dilapidation. Perhaps the English word is a back-formation from dilapidation.
dilapidated (adj.): "in ruins, broken down," 1806, past participle adjective from dilapidate.
dilapidation (n.): early 15c., from Late Latin dilapidationem (nominative dilapidatio) "a squandering," noun of action from past participle stem of Latin dilapidare "throw away, squander, waste," literally "pelt with stones" (thus "ruin, destroy") or else "scatter like stones," from dis- "asunder" (see dis-) + lapidare "throw stones at," from lapis (genitive lapidis) "stone." "Taken in Eng. in a more literal sense than was usual in Latin" [OED].
dilatation (n.): c.1400, from Old French dilatation, from Late Latin dilatationem (nominative dilatatio) "a widening," from past participle stem of Latin dilatare (see dilate).
dilate (v.): late 14c., from Old French dilater, from Late Latin dilatare "make wider, enlarge," from dis- "apart" (see dis-) + latus "wide" (see latitude). Related: Dilated; dilating.
dilation (n.): 1590s, formed from dilate on the mistaken assumption that the -ate in that word was the Latin verbal suffix (it is instead part of the stem); the proper form, dilatation, is older (c.1400).
dilatory (adj.): late 15c., from Late Latin dilatorius, from dilator "procrastinator," from dilatus, serving as past participle of differe "delay" (see defer).
dildo (n.): 1590s, perhaps a corruption of Italian deletto "delight," from Latin dilectio, noun of action from diligere "to esteem highly, to love" (see diligence). Or (less likely) of English diddle. "Curse Eunuke dilldo, senceless counterfet" ["Choise of Valentines or the Merie Ballad of Nash his Dildo," T. Nashe, c.1593]
dilemma (n.): 1520s, from Late Latin dilemma, from Greek dilemma "double proposition," a technical term in rhetoric, from di- "two" + lemma "premise, anything received or taken," from root of lambanein "to take" (see analemma). It should be used only of situations where someone is forced to choose between two alternatives, both unfavorable to him. But even logicians disagree on whether certain situations are dilemmas or mere syllogisms.
dilettante (n.): 1733, borrowing of Italian dilettante "lover of music or painting," from dilettare "to delight," from Latin delectare (see delight (n.)). Originally without negative connotation, "devoted amateur," the pejorative sense emerged late 18c. by contrast with professional.
diligence (n.): mid-14c., from Old French diligence "attention, care; haste, speed," from Latin diligentia "attentiveness, carefulness," from diligentem (nominative diligens) "attentive, assiduous, careful," originally present participle of diligere "single out, value highly, esteem, prize, love; aspire to, be content with, appreciate," originally "to pick out, select," from dis- "apart" (see dis-) + legere "choose, gather" (see lecture (n.)).

Sense evolved from "love" through "attentiveness" to "carefulness" to "steady effort." From the secondary French sense comes the old useage of diligence for "public stage coach" (1742; dilly for short), from a French shortening of carrosse de diligence.
diligent (adj.): mid-14c., from Old French diligent (14c.), from Latin diligentem "attentive, assiduous" (see diligence). Related: Diligently.
dill (n.): Old English dile "dill, anise," a West Germanic word of unknown origin (cf. Old Saxon dilli, Middle Dutch and Dutch dille, Swedish dill, German Dill).
dilly (n.): "delightful or excellent person or thing" (often used ironically), 1935, American English, from an earlier adjective (1909), perhaps from the first syllable of delightful or delicious, or related to the nursery word for "duck." Dilly was also slang for a stagecoach (1818), from French carrosse de diligence (see diligence).
dilly-dally (v.): 1741, probably a reduplication of dally. Related: Dilly-dallying.
dilute (v.): 1550s, from Latin dilutus, past participle of diluere "dissolve, wash away, dilute," from dis- "apart" + -luere, comb. form of lavere "to wash" (see lave). Related: Diluted; diluting. As an adjective from c.1600.
dilution (n.): 1640s, noun of action from past participle stem of Latin diluere (see dilute).
diluvial (adj.): "pertaining to a flood" (or The Flood), 1650s, from Late Latin diluvialis, from Latin diluvium "flood, inundation" (see deluge (n.)). Related: Diluvian.
dim (adj.): Old English dimm "dark, gloomy, obscure," from Proto-Germanic *dimbaz (cf. Old Norse dimmr, Old Frisian dim, Old High German timber "dark, black, somber"). Not known outside Germanic. Slang sense of "stupid" is from 1892. Related: Dimly; dimness.
dim (v.): c.1200, perhaps in Old English, from dim (adj.). Related: Dimmed; dimming.
dim sum (n.): 1948, from Cantonese dim sam (Chinese dianxin) "appetizer," said to mean literally "touch the heart."
dime (n.): chosen 1786 as name for U.S. 10 cent coin, from dime "a tenth, tithe" (late 14c.), from Old French disme (Modern French dîme) "a tenth part," from Latin decima (pars) "tenth (part)," from decem "ten" (see ten).

The verb meaning "to inform" (on someone) is 1960s, from the then-cost of a pay phone call. A dime a dozen "almost worthless" first recorded 1930. Phrase stop on a dime attested by 1954 (a dime being the physically smallest unit of U.S. currency).
dimension (n.): late 14c., "measurement, size," from Latin dimensionem (nominative dimensio) "a measuring," noun of action from past participle stem of dimetri "to measure out," from dis- (see dis-) + metiri "to measure" (see measure). Meaning "any component of a situation" is from 1929. Related: Dimensional; dimensions.
diminish (v.): early 15c., from merger of two obsolete verbs, diminue and minish. Diminue is from Old French diminuer "make small," from Latin diminuere "break into small pieces," variant of deminuere "lessen, diminish," from de- "completely" + minuere "make small" (see minus).

Minish is from Old French menuisier, from Latin minuere. Related: Diminished; diminishes; diminishing.
diminuendo: 1775, from Italian diminuendo "lessening, diminishing," present participle of diminuire, from Latin deminuere (see diminish).
diminution (n.): c.1300, from Anglo-French diminuciun, Old French diminucion, from Latin diminutionem (nominative diminutio), earlier deminutionem, noun of action from past participle stem of deminuere (see diminish).
diminutive: late 14c. (noun and adjective), from Old French diminutif (14c.), from Latin diminutivus, earlier deminutivus, from past participle stem of deminuere (see diminish).
dimity (n.): mid-15c., from Italian dimiti, plural of dimito, a name for a kind of strong cotton cloth, from Medieval Latin dimitum, from Greek dimitos "of double thread," from di- (see di- (1)) + mitos "warp thread, thread" (see mitre).
dimmer (n.): 1822, agent noun from dim (v.). Of mechanisms for reducing the brightness of electric lights, from 1905.
dimorphous (adj.): 1832, from Greek dimorphos "of two forms," from di- (see di- (1)) + morphe "form, shape" (see Morpheus).
dimple (n.): c.1400, perhaps existing in Old English as a word meaning "pothole," perhaps ultimately from Proto-Germanic *dumpilaz, which has yielded words in other languages meaning "small pit, little pool" (e.g. German Tümpel "pool," Middle Low German dümpelen, Dutch dompelen "to plunge"). Related: Dimples.
dimple (v.): 1570s (implied in dimpled), from dimple (n.).
dimwit (n.): also dim-wit, U.S. college slang by 1922, from dim (adj.) + wit (n.). Related: dimwitted.
din (n.): Old English dyne (n.), dynian (v.), from Proto-Germanic *duniz (cf. Old Norse dynr, Danish don, Middle Low German don "noise"), from PIE root *dwen- "to make noise" (cf. Sanskrit dhuni "roaring, a torrent").
Dinah: fem. proper name, in the Old Testament, Jacob's daughter by Leah, from Hebrew Dinah, literally "judgment," from din "to judge."
dinar (n.): Middle Eastern unit of currency, 1630s, from Arabic dinar, from late Greek denarion, from Latin denarius (see denarius).
Dinaric (adj.): from Dinara, ancient name of a mountain in Dalmatia.
dine (v.): late 13c., from Old French disner (Modern French dîner) "to dine, eat, have a meal," originally "take the first meal of the day," from stem of Gallo-Romance *desjunare "to break one's fast," from Vulgar Latin *disjejunare, from dis- "undo" (see dis-) + Late Latin jejunare "to fast," from Latin iejunus "fasting, hungry" (see jejune).
diner (n.): "one who dines, 1815," agent noun from dine. Meaning "railway car for eating" is 1890, American English; of restaurants built to resemble dining cars (or in some cases actual converted dining cars) from 1935. The Diner's Club credit card system dates from 1952.
dinette (n.): 1930, from dine + diminutive (or false French) suffix -ette.
ding (v.): 1819, "to sound as metal when struck," possibly abstracted from ding-dong, of imitative origin. The meaning "to deal heavy blows" is c.1300, probably from Old Norse dengja "to hammer," perhaps also imitative. Meaning "dent" is 1960s. Related: Dinged; dinging.
ding dong: imitative of the sound of a bell, c.1560.
ding-a-ling (n.): "one who is crazy," 1935, from notion of hearing bells in the head (see ding (v.)).