Online Etymology Dictionary

enlightenment (n.): 1660s, "action of enlightening," from enlighten + -ment. Used only in figurative sense, of spiritual enlightenment, etc. Attested from 1865 as a translation of German Aufklärung, a name for the spirit and system of Continental philosophers in the 18c.
The philosophy of the Enlightenment insisted on man's essential autonomy: man is responsible to himself, to his own rational interests, to his self-development, and, by an inescapable extension, to the welfare of his fellow man. For the philosophes, man was not a sinner, at least not by nature; human nature -- and this argument was subversive, in fact revolutionary, in their day -- is by origin good, or at least neutral. Despite the undeniable power of man's antisocial passions, therefore, the individual may hope for improvement through his own efforts -- through education, participation in politics, activity in behalf of reform, but not through prayer. [Peter Gay, "The Enlightenment"]
enlist (v.): 1590s, from en- (1) "make, put in" + list (n.). Possibly suggested by Dutch inlijsten "to write on a list." Related: Enlisted; enlisting.
enlistment (n.): 1765, from enlist + -ment.
enliven (v.): 1630s, "give life to" (enlive in same sense is from 1590s); see en- (1) "make, put in" + life + -en (1). Meaning "make lively or cheerful" is from 1690s. Related: Enlivened; enlivening.
enmesh (v.): c.1600, from en- (1) + mesh (v.). Related: Enmeshed; enmeshing.
enmity (n.): late 14c., from Old French enemistié "enmity, hostile act, aversion," from Vulgar Latin *inimicitatem (nominative *inimicitas), from Latin inimicitia "enmity, hostility," from inimicus "enemy" (see enemy). Related: Enmities.
ennead (n.): "group of nine things," 1650s, from Greek enneas (genitive enneados) "group of nine," from ennea "nine" (cognate with Sanskrit nava, Latin novem, Gothic niun, Old English nigun; see nine).
ennoble (v.): late 15c. (implied in ennobled), from Middle French ennoblir; see en- (1) + noble (adj.). Related: Ennobling.
ennui (n.): 1660s as a French word in English; nativized by 1758; from French ennui, from Old French enui "annoyance" (13c.), back-formation from enuier (see annoy). Hence ennuyé "afflicted with ennui;" ennuyée a woman so afflicted.
So far as frequency of use is concerned, the word might be regarded as fully naturalized; but the pronunciation has not been anglicized, there being in fact no Eng. analogy which could serve as a guide. [OED]
Enoch: masc. proper name, in Old Testament eldest son of Cain, father of Methuselah, from Latin Enoch, from Greek Enokh, from Hebrew Hanokh, literally "dedicated, consecrated," from hanakh "he dedicated," whence also Hanukkah.
enormity (n.): late 15c., "transgression, crime, irregularity," from Old French énormité "extravagance, enormity, atrocity, heinous sin," from Latin enormitatem (nominative enormitas) "hugeness, vastness, irregularity," from enormis (see enormous). Meaning "extreme wickedness" in English attested from 1560s; sense of "hugeness" (1792) is etymological but probably best avoided to prevent misunderstanding.
enormous (adj.): 1530s, from Latin enormis "out of rule, irregular, shapeless, extraordinary, very large," from ex- "out of" (see ex-) + norma "rule, norm" (see norm), with English -ous substituted for Latin -is.

Meaning "extraordinary in size" is attested from 1540s; original sense of "outrageous" is more clearly preserved in enormity. Earlier in same sense was enormyous (mid-15c.). Related: Enormously.
Enos: masc. proper name, in Old Testament the son of Seth, from Greek Enos, from Hebrew Enosh, literally "man" (cf. nashim "women," Arabic ins "men, people").
enough (adj.): c.1300, from Old English genog, a common Germanic formation (cf. Old Saxon ginog, Old Frisian enoch, Dutch genoeg, Old High German ginuog, German genug, Old Norse gnogr, Gothic ganohs).

This is a compound of ge- "with, together" (also a participial, collective, intensive, or perfective prefix) + root -nah, from PIE *nek- "reach, attain" (cf. Sanskrit asnoti "reaches," Hittite ninikzi "lifts, raises," Lithuanian nešti "to bear, carry," Latin nancisci "to obtain").

It is the most prominent among the surviving examples of Old English ge-, the equivalent of Latin com- and Modern German ge-, from PIE *kom- "beside, near, by, with" (see com-).

Meaning "moderately, fairly, tolerably" (good enough) was in Middle English. Understated sense of have had enough "have had too much" was in Old English (which relied heavily on double negatives and understatement). Colloquial 'nough said is attested from 1839.
enow (adj., n.): Old English genoge (plural adjective); see enough. Until 18c., regarded as standard as the plural of enough.
enquire (v.): see inquire. An alternative form mainly used in sense of "to ask a question." Related: enquired; enquiring.
enquiry (n.): alternative spelling of inquiry. Related: Enquiries.
enrage (v.): late 14c. (implied in enraged), from Old French enragier "go wild, go mad, lose one's senses," from en- "make, put in" (see en- (1)) + rage "rabies, rage" (see rage (n.)). Related: Enraging. Intransitive only in Old French; transitive sense is oldest in English.
enrapt (adj.): c.1600, "carried away by (prophetic) ecstasy," past participle adjective from en- "make, put in" (see en- (1)) + rapt (see rapture).
enrapture (v.): 1740, from en- (1) + rapture. Related: Enraptured.
enrich (v.): late 14c., "to make wealthy," from Old French enrichir "enrich, enlarge," from en- "make, put in" (see en- (1)) + riche "rich" (see rich).

Figurative sense is from 1590s. Scientific sense of "to increase the abundance of a particular isotope in some material" is first attested 1945. Related: Enriched; enriching.
enrichment (n.): 1620s, from enrich + -ment.
enrol (v.): alternative spelling of enroll.
enroll (v.): mid-14c., from Old French enroller "record in a register" (13c., Modern French enrôler), from en- "make, put in" (see en- (1)) + rolle (see roll (n.)). Related: Enrolled; enrolling.
enrollment (n.): also enrolment, mid-15c., from Anglo-French enrollement, from Middle French enrollement, from Old French enroller "record in a register" (see enroll).
ensample (n.): "precedent," c.1300, variant of asaumple, from Old French essample "example" (see example). The survival of this variant form is due to its use in New Testament in KJV.
ensconce (v.): 1580s, "to cover with a fort," from en- (1) "make, put in" + sconce "small fortification, shelter," perhaps via French, probably from Dutch schans "earthwork" (cf. Middle High German schanze "bundle of sticks"), of uncertain origin. Related: Ensconced.
ensemble (n.): mid-15c., as an adverb, "together, at the same time," from Middle French ensemblée "all the parts of a thing considered together," from Late Latin insimul "at the same time," from in- intensive prefix + simul "at the same time," related to similis (see similar). The noun is from 1703, "parts of a thing taken together;" musical sense in English first attested 1844. Of women's dress and accessories, from 1927.
enshrine (v.): 1580s, from en- (1) "make, put in" + shrine. Related: Enshrined; enshrining.
enshroud (v.): 1580s, from en- (1) "make, put in" + shroud (n.). Related: Enshrouded; enshrouding.
ensign (n.): late 14c., via Scottish, from Old French enseigne (12c.) "mark, symbol, signal; flag, standard, pennant," from Latin insignia (plural); see insignia. Sense of "banner, flag" is c.1400; that of soldier who carries one is first recorded 1510s. U.S. Navy sense of "commissioned officer of the lowest rank" is from 1862. French navy had rank of enseigne de vaisseau since at least early 18c.
enslave (v.): 1640s, from en- (1) "make, put in" + slave (n.). Related: Enslaved; enslaving.
enslavement (n.): 1690s, from enslave + -ment.
ensnare (v.): 1570s, from en- (1) "make, put in" + snare (n.). Related: Ensnared; ensnaring.
ensue (v.): late 14c., from Old French ensu-, past participle stem of ensivre "follow close upon, come afterward," from Late Latin insequere, from Latin insequi "to pursue, follow, follow after; come next," from in- "upon" (see in- (2)) + sequi "follow" (see sequel). Related: Ensued; ensues; ensuing.
ensure (v.): late 14c., from Anglo-French enseurer, from en- "make" (see en- (1)) + Old French seur "sure" (see sure); probably influenced by Old French asseurer "assure." Related: Ensured; ensures; ensuring.
entablature (n.): 1610s, nativization of Italian intavolatura; see en- (1) + tablature.
entail (v.): mid-14c., "convert (an estate) into 'fee tail' (feudum talliatum)," from en- (1) "make" + taile "legal limitation," especially of inheritance, ruling who succeeds in ownership and preventing it from being sold off, from Anglo-French taile, Old French taillie, past participle of taillier "allot, cut to shape," from Late Latin taliare. Sense of "have consequences" is 1829, from notion of "inseparable connection." Related: Entailed; entailling.
entangle (v.): early 15c., from en- (1) + tangle (n.). Related: Entangled; entangling.
entanglement (n.): 1640s, from entangle + -ment. Foreign entanglements does not appear as such in Washington's Farewell Address, though he nonetheless warns against them. The phrase is found in William Coxe's 1798 memoirs of Sir Robert Walpole.
entelechy (n.): c.1600, from Greek entelekheia, from en "in" (see en- (2)) + telei, dative of telos "perfection" (see tele-) + ekhein "to have" (see scheme (n.)). In Aristotle, "the condition in which a potentiality has become an actuality."
entente (n.): 1854, from French éntente "understanding," from Old French entente "intent" (12c.), noun use of fem. past participle of entendre "to direct one's attention (see intent). Political sense arose in 19c. from entente cordial (1844), the best-known example being that between England and France (1904), to which Russia was added in 1908.
enter (v.): late 13c., from Old French entrer, from Latin intrare "to go into, enter" (source of Spanish entrar, Italian entrare), from intra "within," related to inter (prep., adj.) "among, between" (see inter-). Related: Entered; entering.
enteric (adj.): "pertaining to the intestines," 1869, from Greek enterikos "intestinal," first used in this sense by Aristotle, from entera (plural; singular enteron) "intestines," from PIE *enter-, comparative of *en "in" (see inter-).
enteritis (n.): 1808, medical Latin, coined c.1750 by French pathologist François-Boissier de la Croix de Sauvages (1706-1767), from enteron "intestine" (see enteric) + -itis.
entero-: before vowels enter-, word-forming element meaning "intestine," from comb. form of Greek enteron "an intestine, piece of gut" (see enteric).
enterovirus (n.): 1957; see entero- + virus.
enterprise (n.): early 15c., "an undertaking," from Old French enterprise "an undertaking," noun use of fem. past participle of entreprendre "undertake, take in hand," from entre- "between" (see entre-) + prendre "to take," contraction of prehendere (see prehensile). Abstract sense of "readiness to undertake challenges, spirit of daring" is from late 15c.
enterprising (adj.): "eager to undertake," 1610s, from enterprise. Until mid-19c. (at least in Britain) mostly in a bad sense: "scheming, ambitious, foolhardy." Earlier (1560s) as a verbal noun meaning "action of undertaking."
entertain (v.): late 15c., "to keep up, maintain, to keep (someone) in a certain frame of mind," from Middle French entretenir (12c.), from Old French entretenir "hold together, stick together, support," from entre- "among" (from Latin inter; see inter-) + tenir "to hold" (from Latin tenere; see tenet).

Sense of "have a guest" is late 15c.; that of "amuse" is 1620s. Meaning "to allow (something) to consideration" (of opinions, notions, etc.) is 1610s. Related: Entertained; entertaining.