Online Etymology Dictionary

encapsulation (n.): 1859, "act of surrounding with a capsule," noun of action from encapsulate. Figurative use by 1934.
encase (v.): 1630s, from en- (1) "make, put in" + case (n.2). Related: Encased; encasing.
encaustic: c. 1600 (n.), "art of encaustic painting;" 1650s (adj.) "produced by burning in," from Greek enkaustikos, from enkaiein "to burn in" from en (see en- (2)) + kaiein "to burn" (see caustic). "Strictly applicable only to painting executed or finished by the agency of heat" [Century Dictionary].
enceinte (adj.): "pregnant, with child," c. 1600, insente, from French enceinte "pregnant" (12c.), from Late Latin incincta (source of Italian incinta), explained by Isidore of Seville (7c.) as "ungirt," from Latin in-, privative prefix (see in- (1)), + cincta, fem. of cinctus, past participle of cingere "to gird" (see cinch). But perhaps the Late Latin word is from past participle of Latin incingere "to put into a girdle" (that is, "to make (a woman) pregnant"), with in- (2) "in, into." Modern form is 18c., perhaps a reborrowing from French.
encephalitis (n.): "inflammation of the brain," 1843, from encephalo- "the brain" + -itis "inflammation." Related: Encephalitic.
encephalo-: before vowels encephal-, word-forming element meaning "brain, of the brain," from comb. form of medical Latin encephalon, from Greek enkephalos "the brain," literally "within the head," from en "in" (see en- (2)) + kephale "head;" see cephalo-.
enchain (v.): late 14c., "become linked together;" mid-15c., "to secure with a chain," from Old French enchainer, from Medieval Latin incatenare "enchain," from in (see in) + catenare, from catena "a chain" (see chain (n.)). Related: Enchained; enchaining.
enchant (v.): late 14c., literal and figurative, from Old French enchanter "bewitch, charm, cast a spell" (12c.), from Latin incantare "to enchant, fix a spell upon" (see enchantment). Or perhaps a back-formation from enchantment.
enchanted (adj.): "delighted," 1590s, past participle adjective from enchant (v.).
enchanter (n.): late 13c., agent noun from enchant, or from Old French enchanteor "magician; singer; mountebank," from Latin incantator.
enchanting (adj.): 1590s, "having magical power," present participle adjective from enchant (v.). Meaning "bewitched" is from 1712. Related: Enchantingly.
enchantment (n.): c. 1300, "act of magic or witchcraft; use of magic; magic power," from Old French encantement "magical spell; song, concert, chorus," from enchanter "bewitch, charm," from Latin incantare "enchant, cast a (magic) spell upon," from in- "upon, into" (see in- (2)) + cantare "to sing" (see chant (v.)). Figurative sense of "allurement" is from 1670s. Compare Old English galdor "song," also "spell, enchantment," from galan "to sing," which also is the source of the second element in nightingale.
enchantress (n.): late 14c., "witch," from enchanter + -ess. Meaning "charming woman" is from 1713.
encharge (v.): late 14c., "impose (something) as a duty or obligation," from Old French enchargier, from Medieval Latin incaricare "load, charge," from in- "in" (see in- (2)) + caricare "to load," from Vulgar Latin carricare "to load a car" (see charge (v.)).
enchilada (n.): 1876, American English, from Mexican Spanish enchilada, fem. past participle of enchilar "season with chili," from en- "in" + chile "chili" (see chili).
You never ate enchilada, did you? I hope you never will. An enchilada looks not unlike an ordinary flannel cake rolled on itself and covered with molasses. The ingredients which go to make it up are pepper, lye, hominy, pepper, onions chopped fine, pepper, grated cheese, and pepper. ["The Health Reformer," December 1876]
enchiridion (n.): 1540s, "a handbook," from Late Latin, from Greek enkheiridion, neuter of enkheiridios "that which is held in the hand," from en "in" (see en- (2)) + kheir "hand" (see chiro-) + diminutive suffix -idion.
encircle (v.): c. 1400, from en- (1) "make, put in" + circle (n.). Related: Encircled; encircling.
encirclement (n.): 1809, from encircle + -ment.
enclave (n.): "small portion of one country which is entirely surrounded by the territory of another," 1868, from French enclave, from Old French enclaver "enclose, comprise, include" (13c.), from Late Latin inclavare "shut in, lock up," from Latin in- "in" (see in- (2)) + clavis "key" (see slot (n.2)). Enclaved "surrounded by land owned by another" is attested in English from mid-15c., from Old French enclaver.
enclitic: 1650s (adj.); 1660s (n.), in grammar, from Late Latin encliticus, from Greek enklitikos "throwing its accent back," literally "leaning on," from verbal adjectival stem of enklinein "to bend, lean on," from en "in" (see en- (2)) + klinein "to lean" (see lean (v.)).
enclose (v.): early 14c., from en- (1) + close, and partially from Old French enclos, past participle of enclore "surround; confine; contain." Specific sense of "to fence in waste or common ground" for the purpose of cultivation or to give it to private owners is from c. 1500. Meaning "place a document with a letter for transmission" is from 1707. Related: Enclosed; enclosing.
enclosure (n.): mid-15c., "action of enclosing," from enclose + -ure. Meaning "that which is enclosed" is from 1550s.
encode (v.): 1917, from en- (1) "make, put in" + code (n.). Computing sense is from 1955, usually shortened colloquially or for clarity to code. Related: Encoded; encoding.
encomiast (n.): c. 1600, from Greek enkomiastes "one who praises," from enkomiazein, from enkomion (see encomium). Related: Encomiastic (1590s).
encomienda (n.): "estate granted to a Spaniard in America with powers to tax the Indians," 1810, from Spanish, literally "commission," from or related to encomendar "to commit, charge," from assimilated form of Latin in- "in" (see in- (2)) + Medieval Latin commendam, from Latin commendare "commit to one's care, commend" (see commend).
encomium (n.): "discriminating expression of approval," 1580s, from Late Latin encomium, from Greek enkomion (epos) "laudatory (ode), eulogy," from en "in" (see en- (2)) + komos "banquet, procession, merrymaking" (see comedy).
encompass (v.): 1550s, from en- (1) "make, put in" + compass (n.). Related: Encompassed; encompasses; encompassing.
encore (interj.): 1712, from French encore "still, yet, again, also, furthermore" (12c.), generally explained as being from Vulgar Latin phrase *hinc ad horam "from then to this hour," or (in) hanc horam "(to) this hour" (Italian ancora "again, still, yet" is said to be a French loan-word).
Whenever any Gentlemen are particularly pleased with a Song, at their crying out Encore ... the Performer is so obliging as to sing it over again. [Steele, "Spectator" No. 314, 1712]

There appears to be no evidence that either the Fr. or It. word was ever similarly used in its native country. The corresponding word both in Fr. and It. is bis; in It. da capo was formerly used. [OED]
As a noun, from 1763; as a verb, from 1748. Related: Encored.
encounter (n.): c. 1300, "meeting of adversaries, confrontation," from Old French encontre "meeting; fight; opportunity" (12c.), noun use of preposition/adverb encontre "against, counter to" from Late Latin incontra "in front of," from Latin in- "in" (see in- (2)) + contra "against" (see contra). Modern use of the word in psychology is from 1967, from the work of U.S. psychologist Carl Rogers (1902-1987). Encounter group attested from 1967.
encounter (v.): c. 1300, "to meet as an adversary," from Old French encontrer "meet, come across; confront, fight, oppose," from encontre (see encounter (n.)). Weakened sense of "meet casually or unexpectedly" first recorded in English early 16c. Related: Encountered; encountering.
encourage (v.): early 15c., from Old French encoragier "make strong, hearten," from en- "make, put in" (see en- (1)) + corage "courage, heart" (see courage). Related: Encouraged; encouraging; encouragingly.
encouragement (n.): 1560s, from encourage + -ment, or from Middle French encoragement.
As a general rule, Providence seldom vouchsafes to mortals any more than just that degree of encouragement which suffices to keep them at a reasonably full exertion of their powers. [Hawthorne, "House of Seven Gables"]
encrease: obsolete or archaic form of increase.
encroach (v.): late 14c., "acquire, get," from Old French encrochier "seize, fasten on, hang on (to), cling (to); hang up, suspend," literally "to catch with a hook," from en- "in" (see en- (1)) + croc "hook," from Old Norse krokr "hook" (see crook (n.)). Sense extended to "seize wrongfully" (c. 1400), then "trespass" (1530s). Related: Encroached; encroaches; encroaching.
encroachment (n.): mid-15c., "obtruding structure," from encroach + -ment, or an equivalent Old French compound.
encrust (v.): also incrust, 1640s, from Middle French encruster, incruster (Modern French encroûter), from Latin incrustare "to coat or cover with crust," from in- (see in- (2)) + crusta (see crust (n.)). Related: Encrusted; encrusting.
encrypt (v.): 1968 in telecommunications, a back-formation from encryption (1964), or from en- (1) + crypt (n.) on the notion of "hidden place" (see crypto-). Related: Encrypted; encrypting.
enculturation (n.): 1948 (Herskovits), from en- (1) + culturation (compare acculturation).
encumber (v.): early 14c., "burden, vex, inconvenience," from Old French encombrer "to block up, hinder, thwart," from Late Latin incombrare, from in- "in" (see in- (2)) + combrus "barricade, obstacle," probably from Latin cumulus "heap" (see cumulus). Meaning "hinder, hamper" is attested in English from late 14c. Related: Encumbered; encumbering.
encumbrance (n.): c. 1300, "trouble, difficulty; ensnarement, temptation," from Old French encombrance "encumbrance, obstruction; calamity, trouble," from encombrer (see encumber). Meaning "that which encumbers, impediment, obstacle" is from late 14c. in English.
encyclical (adj.): in reference to ecclesiastical letters meant for wide circulation (for example, a letter sent by a pope to all bishops), 1640s, from Late Latin encyclicus, from Latin encyclius, from Greek enkyklios "in a circle, circular" (see encyclopedia). As a noun, from 1837.
encyclopaedia (n.): see encyclopedia. The Latin spelling survives as a variant because many of the most prominent ones (such as Britannica) have Latin names.
encyclopedia (n.): 1530s, "general course of instruction," from Modern Latin encyclopaedia (c. 1500), thought to be a false reading by Latin authors of Greek enkyklios paideia taken as "general education," but literally "training in a circle," i.e. the "circle" of arts and sciences, the essentials of a liberal education; from enkyklios "circular," also "general" (from en "in;" see in + kyklos "circle;" see cycle (n.)) + paideia "education, child-rearing," from pais (genitive paidos) "child" (see pedo-).

Modern sense of "reference work arranged alphabetically" is from 1640s, often applied specifically to the French "Encyclopédie ou Dictionnaire raisonné des Sciences, des Arts, et des Métiers" (1751-65). Related: Encyclopedist.
encyclopedic (adj.): 1816, from encyclopedia + -ic.
end (n.): Old English ende "end, conclusion, boundary, district, species, class," from Proto-Germanic *andja (source also of Old Frisian enda, Old Dutch ende, Dutch einde, Old Norse endir "end;" Old High German enti "top, forehead, end," German Ende, Gothic andeis "end"), originally "the opposite side," from PIE *antjo "end, boundary," from root *ant- "opposite, in front of, before" (see ante).
Worldly wealth he cared not for, desiring onely to make both ends meet. [Thomas Fuller, "The History of the Worthies of England," 1662]
Original sense of "outermost part" is obsolete except in phrase ends of the earth. Sense of "destruction, death" was in Old English. Meaning "division or quarter of a town" was in Old English. The end "the last straw, the limit" (in a disparaging sense) is from 1929. The end-man in minstrel troupes was one of the two at the ends of the semicircle of performers, who told funny stories and cracked jokes with the middle-man. U.S. football end zone is from 1909 (end for "side of the field occupied by one team" is from 1851). The noun phrase end-run is attested from 1893 in U.S. football; extended to military tactics by 1940. End time in reference to the end of the world is from 1917. To end it all "commit suicide" is attested by 1911. Be-all and end-all is from Shakespeare ("Macbeth" I.vii.5).
end (v.): Old English endian "to end, finish, abolish, destroy; come to an end, die," from the source of end (n.). Related: Ended; ending.
end-paper (n.): in book-binding, "blank leaves before and after the text of a book," 1818, from end (n.) + paper (n.).
endanger (v.): late 15c., from en- (1) "make, put in" + danger. Related: Endangered; endangering. Endangered species recorded by 1958.
endangerment (n.): 1640s (Milton), from endanger + -ment. Earlier was endangering (1580s).
endear (v.): 1580s, "to enhance the value of," also "win the affection of," from en- (1) "make, put in" + dear (adj.). Meaning "to make dear," the main modern sense, is from 1640s. Related: Endeared; endearing.