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Dexter [Dexter 词源字典]: masc. proper name, from Latin dexter "on the right hand" (see dexterity). Compare also Benjamin.[Dexter etymology, Dexter origin, 英语词源]
dexterity (n.): 1520s, from Middle French dexterité (16c.), from Latin dexteritatem (nominative dexteritas) "readiness, skillfulness, prosperity," from dexter "skillful," also "right (hand)" (source of Old French destre, Spanish diestro, etc.), from PIE root *deks- "on the right hand," hence "south" to one facing east (cognates: Sanskrit daksinah "on the right hand, southern, skillful;" Avestan dashina- "on the right hand;" Greek dexios "on the right hand," also "fortunate, clever;" Old Irish dess "on the right hand, southern;" Welsh deheu; Gaulish Dexsiva, name of a goddess of fortune; Gothic taihswa; Lithuanian desinas; Old Church Slavonic desnu, Russian desnoj). The Latin form is with the comparative suffix -ter, thus meaning etymologically "the better direction." Middle English dester meant "right hand," and in heraldry dexter means "on the right side."
dexterous (adj.): c. 1600, "convenient, suitable," formed in English from Latin dexter (see dexterity) + -ous. Meaning "skillful, clever" is from 1620s.
dextro-: word-forming element meaning "toward or on the right-hand side," from comb. form of Latin dexter (see dexterity).
dextrose (n.): 1867, shortened from dextro-glucose, from dextro- "right" + -ose (2), chemical suffix indicating a sugar. So called because this form of glucose polarizes light to the right in spectroscopy.
dextrous (adj.): 1620s, alternative spelling of dexterous; this version is more conformable to Latin but less common in English.
dey (n.1): Old English dæge "female servant, housekeeper, maid," from Proto-Germanic *daigjon (cognates: Old Norse deigja "maid, female servant," Swedish deja "dairymaid"), from PIE *dheigh- "to form, build" (see dough). Now obsolete (though OED says, "Still in living use in parts of Scotland"), it forms the first element of dairy and the second of lady.

The ground sense seems to be "kneader, maker of bread;" advancing by Old Norse deigja and Middle English daie to mean "female servant, woman employed in a house or on a farm." Dæge as "servant" is the second element in many surnames ending in -day (such as Faraday, and perhaps Doubleday "servant of the Twin," etc.).
dey (n.2): 1650s, "title of a military commander in Muslim north Africa," from Turkish dai "maternal uncle," a friendly title used of older men, especially by the Janissaries of Algiers of their commanding officers. There were also deys in Tunis and Tripoli.
dharma (n.): 1796, in secular sense, "caste custom, right behavior;" in Buddhism and Hinduism, "moral law," from Sanskrit, "law, right, justice," related to dharayati "holds," and cognate with Latin firmus, all from PIE root *dher- (2) "to hold firmly, support" (see firm (adj.)).
dhoti: 1620s, from Hindi dhoti.
dhow (n.): 1799, original language unknown, "single-masted native vessel used on Arabian Sea," later widely applied to all Arab vessels. Klein suggests a relation to Persian dav "running."
di- (1): word-forming element meaning "two, double, twice," from Greek di-, from dis "twice," related to duo (see two).
di- (2): word-forming element meaning "apart, asunder," form of dis- before certain voiced consonants.
di- (3): word-forming element meaning "through; thoroughly," form of dia- before vowels.
dia-: before vowels, di-, word-forming element meaning "through, thoroughly, entirely," from Greek dia-, from dia "through, throughout," probably from the root of duo "two" (see two) with a base sense of "twice."
diabetes (n.): 1560s, from medical Latin diabetes, from late Greek diabetes "excessive discharge of urine" (so named by Aretaeus the Cappadocian, physician of Alexandria, 2c.), literally "a passer-through, siphon," from diabainein "to pass through," from dia- "through" (see dia-) + bainein "to go" (see come).

An old common native name for it was pissing evil. In classical Greek, diabainein meant "to stand or walk with the legs apart," and diabetes meant "a drafting compass," from the position of the legs.
diabetic (adj.): 1799; see diabetes + -ic. From 1840 as a noun.
diabolic (adj.): late 14c., from Old French diabolique (13c.), from Late Latin diabolicus, from Ecclesiastical Greek diabolikos "devilish," from diabolos (see devil (n.)).
diabolical (adj.): c. 1500, "pertaining to the devil," from diabolic + -al (1). Meaning "befitting the devil" is from 1540s. Related: Diabolically.
diabolism (n.): c. 1600s, from Ecclesiastical Greek diabolos "devil" (see devil (n.)) + -ism.