Online Etymology Dictionary

enunciative (adj.): 1530s, from Latin enuntiativus, from enuntiare (see enunciate).
enuresis (n.): 1800, medical Latin, from Greek enourein "to urinate in," from en "in" (see en- (2)) + ourein "to urinate," from ouron (see urine).
envelop (v.): late 14c., envolupen, "be involved in," from Old French envoleper (10c., Modern French envelopper) "envelop, cover; fold up," from en- "in" (see en- (1)) + voloper "wrap up," of uncertain origin, perhaps Celtic (see Gamillscheg, Diez). Literal sense is from 1580s. Related: Enveloped; enveloping.
envelope (n.): 1705, from French enveloppe (13c.), a back-formation from envelopper "to envelop" (see envelop).
envelopment (n.): 1763, from envelop (v.) + -ment.
envenom (v.): c.1300, envenymen, from Old French envenimer (12c.) "to poison, taint;" from en- (see en- (1)) + venim (see venom). Figurative use is from late 14c. Related: Envenomed; envenoming.
enviable (adj.): c.1600, from envy + -able. Related: Enviably.
envious (adj.): c.1300, from Anglo-French envious, Old French envieus (13c.), earlier envidius (12c., Modern French envieux), from Latin invidiosus "full of envy" (source of Spanish envidioso, Italian invidioso, Portuguese invejoso), from invidia (see envy). Related: Enviously; enviousness.
environ (v.): late 14c. (implied in environing), "to surround," from Old French environer "to surround, enclose, encircle," from environ "round about," from en- "in" (see en- (1)) + viron "circle, circuit," from virer "to turn" (see veer). Related: Environed.
environment (n.): c.1600, "state of being environed" (see environ + -ment); sense of "nature, conditions in which a person or thing lives" first recorded 1827 (used by Carlyle to render German Umgebung); specialized ecology sense first recorded 1956.
environmental (adj.): 1887, from environment + -al (1). Related: Environmentally (1884).
environmentalism (n.): 1923, as a psychological theory (in the nature vs. nurture debate), from environmental + -ism. The ecological sense is from 1972. Related: Environmentalist (n.), 1916 in the psychological sense, 1970 in the ecological sense.
environs (n.): "outskirts," 1660s, from French environs, plural of Old French environ "compass, circuit," from environ (adv.) "around, round about" (see environ).
envisage (v.): 1778, from French envisager "look in the face of," from en- "cause to" (see en- (1)) + visage "face" (see visage). Related: Envisaged; envisaging.
envision (v.): 1914, from en- (1) "make, put in" + vision. Related: Envisioned; envisioning. Earlier (1827) is envision'd in sense "endowed with vision."
envoy (n.): "messenger," 1660s, from French envoyé "messenger," literally "one sent" (12c.), noun use of past participle of envoyer "send," from Vulgar Latin *inviare "send on one's way," from Latin in "on" (see in- (2)) + via "road" (see via (adv.)). The same French word was borrowed in Middle English to mean "a stanza of a poem sending it off to find readers" (late 14c.).
envy (n.): late 13c., from Old French envie "envy, jealousy, rivalry" (10c.), from Latin invidia "envy, jealousy," from invidus "envious," from invidere "envy," earlier "look at (with malice), cast an evil eye upon," from in- "upon" (see in- (2)) + videre "to see" (see vision).

Similar formations in Avestan nipashnaka "envious," also "look at;" Old Church Slavonic zavideti "to envy," from videti "to see;" Lithuanian pavydeti "to envy," related to veizdeti "to see, to look at."
envy (v.): late 14c., from Old French envier, from envie (see envy (n.)). Related: Envied; envying.
enwind (v.): 1590s (implied in inwinding), from en- (1) + wind (v.). Related: Enwound; enwinding.
enwrap (v.): late 14c., from en- (1) "make, put in" + wrap (v.). Related: Enwrapped; enwrapping.
enzyme (n.): 1881, as a biochemical term, from German Enzym, coined 1878 by German physiologist Wilhelm Kühne (1837-1900), from Modern Greek enzymos "leavened," from en "in" (see en- (2)) + zyme "leaven" (see zymurgy).
eo-: word-forming element used from mid-19c. (first in Eocene) in compound words formed by earth-scientists and meaning "characterized by the earliest appearance of," from Greek eos "dawn," from PIE *aus-, cognate with Modern English east (q.v.). Piltdown Man, before exposed as a fraud, was known as Eoanthropus.
Eocene (adj.): in reference to the second epoch of the Tertiary Period, coined in English 1831, from eo- + Greek kainos "new" (see recent); along with Miocene and Pliocene, by the Rev. William Whewell (1794-1866), English polymath.
Eohippus (n.): oldest known genus of the horse family, 1879, from Modern Latin, from Greek eos (see eo-) + hippos "horse" (see equine).
eolian (adj.): see Aeolian.
eolithic (adj.): 1890, from French éolithique (1883), from eo- (see eo-) + French lithique, as in néolithique (see neolithic). Related: eolith (1890).
eon (n.): 1640s, from Latin aeon, from Greek aion "age, vital force, a period of existence, lifetime, generation;" in plural, "eternity," from PIE root *aiw- "vital force, life, long life, eternity" (cf. Sanskrit ayu "life," Avestan ayu "age," Latin aevum "space of time, eternity," Gothic aiws "age, eternity," Old Norse ævi "lifetime," German ewig "everlasting," Old English a "ever, always").
EPA: initialism for Environmental Protection Agency, U.S. federal agency proposed by President Richard Nixon and created in December 1970.
epact (n.): 1550s, "number of days by which the solar year exceeds a lunar one of 12 moons;" also "number of days into the moon on which the solar year begins;" from French épacte (12c.), from Late Latin epacta "an intercalary day," from Greek epaktos, literally "brought in, inported," verbal adjective of epagein "to intercalate, add, bring forward," from epi "on" (see epi-) + agein "to bring, to lead" (see act (v.)).
epaulet (n.): 1783, from French épaulette (16c.), diminutive of épaule "shoulder," from Old French espaule (12c.), from Latin spatula "flat piece of wood, splint," later "shoulder blade," diminutive of spatha "broad wooden instrument, broad sword," from Greek spathe "a broad flat sword" (see spade (n.1)).
epee (n.): 1889, from French épée, literally "sword" from Old French espe (9c., spede) "spear, lance," from Latin spatha (see epaulet).
epeiric (adj.): in reference to seas covering continental shelves, 1917, from Greek epeiros "mainland" + -ic.
epexegesis (n.): "words added to convey more clearly the meaning intended," 1620s, from Greek epexegesis, from epi "in addition" (see epi) + exegeisthai "to explain" (see exegesis).
ephah (n.): Hebrew dry measure, probably of Egyptian origin.
ephebic (adj.): 1880 (the noun, ephebe, is attested from 1690s), from Greek ephebos "of age 18-20," from epi "upon" (see epi-) + hebe "early manhood," from PIE *yegw-a- "power, youth, strength." In classical Athens, a youth of 18 underwent his dokimasia, had his hair cut off, and was enrolled as a citizen. His chief occupation for the next two years was garrison duty.
ephedra (n.): genus of low, branchy desert shrubs, 1914, from Modern Latin (1737) from Greek ephedra, a name given by Pliny to the horsetail, literally "sitting upon," from fem. of ephedros, from epi "on" (see epi-) + hedra "seat, base, chair, face of a geometric solid" (see sedentary). The reason for the name is not known.
ephedrine (n.): 1889, named 1887 by Japanese organic chemist Nagai Nagayoshi (1844-1929), from the plant ephedra, from which it was first extracted, + chemical suffix -ine (2).
ephemera (n.): late 14c., originally a medical term, from Medieval Latin ephemera (febris) "(fever) lasting a day," from fem. of ephemerus, from Greek ephemeros "lasting only one day, short-lived," from epi "on" (see epi-) + hemerai, dative of hemera "day," from PIE *amer- "day."

Sense extended 17c. to short-lived insects and flowers; general sense of "thing of transitory existence" is first attested 1751. Cf. Greek ephemeroi "men," literally "creatures of a day."
ephemeral (adj.): 1560s; see ephemera + -al (1). Related: Ephemerality. Originally of diseases and lifespans; extended sense of "transitory" is from 1630s.
ephemeris (n.): table showing predicted positions of heavenly bodies, 1550s, Modern Latin, from Greek ephemeris "diary, calendar," from ephemeros "daily" (see ephemera). The classical plural is ephemerides.
ephemeron (n.): 1620s, from Greek (zoon) ephemeron, neuter of ephemeros (see ephemera). Figurative use by 1771.
Ephesians (n.): New Testament epistle, late 14c., addressed to Christian residents of the Greek city of Ephesus, in what is now western Turkey.
Ephesus: Greek city in ancient Asia Minor, center of worship for Artemis, Greek Ephesos, traditionally derived from ephoros "overseer," in reference to its religious significance, but this might be folk etymology.
ephialtes (n.): nightmare or demon that causes nightmares, c.1600, from Greek Ephialtes, name of a demon supposed to cause nightmares; the ancient explanation is that it was from ephallesthai "to leap upon," but OED finds "considerable" phonological difficulties with this.
ephod (n.): Hebrew ephod, from aphad "to put on."
ephor (n.): "Spartan magistrate," 1580s, from Greek ephoros "overseer," from epi- "over" (see epi-) + horan "to see" (see warrant (n.)).
Ephraim: masc. personal name, in Old Testament, younger son of Joseph; also the tribe descended from him, sometimes used figuratively for "Kingdom of Israel;" Greek form of Hebrew Ephrayim, a derivative of parah "was fruitful" (related to Aramaic pera "fruit").
epi-: word-forming element meaning "on, upon, above," also "in addition to; toward, among," from Greek epi "upon, at, close upon (in space or time), on the occasion of, in addition," from PIE *epi, *opi "near, at, against" (cf. Sanskrit api "also, besides;" Avestan aipi "also, to, toward;" Armenian ev "also, and;" Latin ob "toward, against, in the way of;" Oscan op, Greek opi- "behind;" Hittite appizzis "younger;" Lithuanian ap- "about, near;" Old Church Slavonic ob "on"). Before unaspirated vowels, reduced to ep-; before aspirated vowels, eph-. A productive prefix in Greek; also used in modern scientific compounds (e.g. epicenter).
epic (adj.): 1580s, perhaps via Middle French épique or directly from Latin epicus, from Greek epikos, from epos "word, story, poem," from PIE *wekw- "to speak" (see voice). Extended sense of "grand, heroic" first recorded in English 1731. The noun meaning "an epic poem" is first recorded 1706.
epicene (adj.): mid-15c., epycen, originally a grammatical term for nouns that may denote either gender, from Latin epicoenus "common," from Greek epikoinos "common to many, promiscuous," from epi "on" (see epi-) + koinos "common" (see coeno-). Extended sense of "characteristic of both sexes" first recorded in English c.1600; that of "effeminate" 1630s.