Online Etymology Dictionary

lemonade (n.): 1660s, nativized from French limonade (17c.), which is from Italian limonata or else a French formation from limon; see lemon (n.1) + -ade. The earlier English spelling was lemonado (c. 1640) with false Spanish ending.
lemony (adj.): "resembling or infused with lemon," 1846, from lemon (n.1) + -y (2). In Australia/New Zealand slang, also "irritated, angry" (1941). An earlier adjective was lemonish (1719).
lemur (n.): nocturnal Madagascar mammal, 1795, given this sense by Linnaeus, from Latin lemures (plural, singular lemurum) "evil spirits of the dead" in Roman mythology, a word of uncertain origin. De Vaan finds it likely that it and Greek lamia are borrowings of a non-Indo-European (perhaps Anatolian/Etruscan) word for malevolent spirits.
The oldest usage of "lemur" for a primate that we are aware of is in Linnaeus's catalog of the Museum of King Adolf Frederick of Sweden (Tattersall, 1982); .... In this work, he explained his use of the name "lemur" thus: "Lemures dixi hos, quod noctu imprimis obambulant, hominibus quodanmodo similes, & lento passu vagantur [I call them lemurs, because they go around mainly by night, in a certain way similar to humans, and roam with a slow pace]" [Dunkel, Alexander R., et al., "Giant rabbits, marmosets, and British comedies: etymology of lemur names, part 1," in "Lemur News," vol. 16, 2011-2012, p.65]
Lemuria: 1864, name given by English zoologist Philip L. Sclater (1829-1913) to an ancient continent or land bridge, now sunk in the Indian Ocean, connecting Africa, Madagascar, India, and Southeast Asia, which he hypothesized to explain the geographical distribution of mammals around it, especially the lemur, hence the name (with -ia). The premise was considered scientifically untenable by 1880 and the phenomena now are accounted for otherwise, but Lemuria in some ways by chance anticipated Gondwanaland (1896) in the continental drift model.

Earlier Lemuria was the name of the Roman feast of the Lemures, evil spirits of the dead in Roman mythology. The head of each household ritually exorcised them every 9th, 11th, and 13th of May. Related: Lemurian
Lena: fem. proper name, originally a shortened form of Helena or Magdalena.
Lenape: 1728, from the Unami Delaware (Algonquian) native designation, said to mean literally "original person," from /len-/ "ordinary, real, original" + /-a:p:e/ "person." Sometimes in extended form Lenni Lenape, with /leni-/ "real."
lend (v.): "grant temporary possession of," late 14c., from past tense of Old English lænan "to grant temporarily, lease out, make loans, lend money at interest," from Proto-Germanic *laihwnjan, verb derived from *loikw-nes-, the prehistoric source of Old English læn "gift" (see loan (n.)). Compare Dutch lenen, Old High German lehanon, German lehnen, all verbs derived from nouns. In Middle English the past tense form, with terminal -d, became the principal form on analogy of bend, send, etc. To lend an ear "listen" is from late 14c.
lend (n.): "a loan," 1570s, from lend (v.). OED describes it as Scottish and Northern.
lender (n.): mid-15c., agent noun from lend (v.). Old English had laenere, agent noun from lænan; the Middle English word might be a new formation or it might be the older word with an intrusive -d- from lend.
length (n.): Old English lengðu "property of being long or extended in one direction; distance along a line," from Proto-Germanic *langitho, abstract noun from *langaz "long" (root of Old English lang; see long (adj.)) + *-itho, abstract noun suffix (see -th (2)). Cognate with Old Norse lengd, Old Frisian lengethe, Dutch lengte.

Figurative sense of "the distance one goes, extremity to which something is carried" is from 1690s. Phrase at length "to full extent" is attested from c. 1500. As "the length of a swimming pool," 1903. From the notion of "a piece or portion of the extent of anything" come the theater slang sense "a 42-line portion of an actor's part" (1736) and the sporting sense "the length of a horse, car, etc. in a race" used as a unit of measure (1650s).
lengthen (v.): late 14c., "to make longer," also "to grow longer," from length + -en (1). Related: Lengthened; lengthening. Earlier verb was simply length (c. 1300).
lengthways (adv.): 1590s, from length + way (n.) + adverbial genitive -s.
lengthwise (adv.): "in the direction of the length," 1570s, from length + wise (n.). As an adjective by 1871.
lengthy (adj.): "having length" (especially "immoderately long"), 1759, American English, from length + -y (2). Until c. 1840 always characterized in British English as an Americanism.
This word has been very common among us, both in writing and in the language of conversation; but it has been so much ridiculed by Americans as well as Englishmen, that in writing it is now generally avoided. Mr. Webster has admitted it into his dictionary; but as need hardly be remarked it is not in any of the English ones. It is applied by us, as Mr. Webster justly observes, chiefly to writings or discourses. Thus we say, a lengthy pamphlet, a lengthy sermon, &c. The English would say, a long or (in the more familiar style) a longish sermon. [John Pickering, "A Vocabulary, or Collection of Words and Phrases Which Have Been Supposed to be Peculiar to the United States of America," Boston, 1816]
Related: Lengthily; lengthiness.
lenience (n.): 1796, from lenient + -ence.
leniency (n.): 1780, from lenient + -cy.
lenient (adj.): 1650s, "relaxing, soothing" (a sense now archaic), from Middle French lenient, from Latin lenientem (nominative leniens), present participle of lenire "to soften, alleviate, allay; calm, soothe, pacify," from lenis "mild, gentle, calm," which probably is from PIE root *le- (2) "to let go, slacken" (source also of Lithuanian lenas "quiet, tranquil, tame, slow," Old Church Slavonic lena "lazy," Latin lassus "faint, weary," Old English læt "sluggish, slow," lætan "to leave behind").

The usual modern sense of "mild, merciful" (of persons or actions) is first recorded 1787. In earlier use was lenitive, attested from early 15c. of medicines, 1610s of persons. Related: Leniently.
Lenin: pseudonym or alias chosen c. 1902 (for publishing clandestine political works in exile) by Russian revolutionary Vladimir Il'ich Ulyanov (1870-1924). Related: Leninist (1917); Leninism (1918). Leningrad was the name of Russian St. Petersburg from 1924 to 1991.
lenitive (adj.): "assuaging, palliating," early 15c., from Medieval Latin lenitivus, from Latin lenitus, past participle of lenire "to soften, alleviate, pacify" (see lenient). As a noun, "a lenitive medicine," from early 15c.
lenity (n.): "softness, smoothness, mildness," early 15c., from Old French lénité or directly from Latin lenitatem (nominative lenitas) "softness, smoothness, gentleness, mildness," from lenis "soft, mild" (see lenient).
lens (n.): 1690s, "glass to regulate light rays," from Latin lens (genitive lentis) "a lentil," on analogy of the double-convex shape. See lentil. Anatomical use, of the eye part, from 1719. Lens-cap is from 1857.
In the vernacular of the photographer, anyone crowding to the front of a group, staring into the lens, or otherwise attracting attention to himself is known as a "lens louse." ["American Photography," vol. 40, 1946; the term dates from 1915]
Lent (n.): "period between Ash Wednesday and Easter," late 14c., short for Lenten (n.) "the forty days of fasting before Easter" in the Christian calendar (early 12c.), from Old English lencten "springtime, spring," the season, also "the fast of Lent," from West Germanic *langitinaz "long-days," or "lengthening of the day" (source also of Old Saxon lentin, Middle Dutch lenten, Old High German lengizin manoth). This prehistoric compound probably refers to increasing daylight in spring and is reconstructed to be from *langaz "long" (source of long (adj.)) + *tina- "day" (compare Gothic sin-teins "daily"), which is cognate with Old Church Slavonic dini, Lithuanian diena, Latin dies "day" (see diurnal).

Compare similar form evolution in Dutch lente (Middle Dutch lentin), German Lenz (Old High German lengizin) "spring." But the Church sense is peculiar to English. The -en in Lenten (n.) was perhaps mistaken for an affix.
Lenten (adj.): late Old English lencten "pertaining to Lent," from Lent + -en (2). Elizabethan English had Lenten-faced "lean and dismal" (c. 1600).
lenticular (adj.): "lens-shaped, having the form of a double-convex lens," early 15c., from Late Latin lenticularis "lentil-shaped," from lenticula "a small lentil," diminutive of Latin lens "a lentil" (see lentil). Related: Lenticularity (1890).
lentil (n.): type of annual leguminous plant, also its edible seed, mid-13c., from Old French lentille "lentil," also "a freckle" (12c.), from Latin lenticula, diminutive of Latin lens (genitive lentis) "lentil plant, a lentil," cognate with Greek lathyros "pulse;" Old High German German linsa, German linse "a lentil;" Old Church Slavonic lęšta, Russian ljač.
The similarity between Slavic, Gm. and Latin seems too great to be coincidental, but a common preform cannot be reconstructed. Like other agricultural terms, 'lentil' may have been borrowed from a non-IE language in Europe. [de Vaan]
lento (adv.): "slowly" (musical direction), 1724, from Italian lento "slow," from Latin lentus "flexible, pliant, slow, sluggish," from PIE root *lent- "flexible" (see lithe). Related: Lentissimo; lentando ("with increasing slowness").
Leo: zodiac constellation, late Old English, from Latin leo "lion" (see lion). Meaning "person born under the sign of Leo" is from 1894. Leonid "meteor which appears to radiate from Leo" is from 1868. The annual shower peaks Nov. 14.
Leon: medieval kingdom in northwestern Spain, said to be from Latin legionis (septimae) "of the Seventh Legion," which was founded in Spain in 65 B.C.E.; if so the name probably then was conformed to Spanish leon "lion." Related: Leonese.
Leonard: masc. proper name, from French Léonard, Old French Leonard, from German Leonhard, from Old High German *Lewenhart, literally "strong as a lion," from lewo (from Latin Leo, see lion) + hart "hard" (see hard (adj.)).
leonine (adj.): "lion-like," late 14c., from Old French leonin or directly from Latin leoninus "belonging to or resembling a lion," from leo (genitive leonis) "lion." Weekley thinks that Leonine verse (1650s), rhymed in the middle as well as the end of the line, probably is from the name of some medieval poet, perhaps Leo, Canon of St. Victor, Paris, 12c.
leopard (n.): late 13c. (early 13c. as a surname), "large cat of the wooded country of Africa and South Asia," from Old French lebard, leupart "leopard," heraldic or real (12c., Modern French léopard), from Late Latin leopardus, literally "lion-pard, lion-panther" (the animal was thought in ancient times to be a hybrid of these two species), from Greek leopardos, from leon "lion" (see lion) + pardos "male panther," which generally is said to be connected to Sanskrit prdakuh "panther, tiger."

Largest spotted cat of the Old World, the name later also was applied to big cats in the Americas. The word is widespread in Europe: Dutch luipaard, German, Danish leopard, Spanish, Italian leopardo. Middle English spelling variants included lubard, lebarde, lypard, lyepart. Proverbial references to its inability to change its spots are from Jeremiah xiii:23. In Middle English the word is used often in heraldry, but there it refers to a lion passant gardant (as on the emblem of Edward the Black Prince).
Leopold: masc. proper name, from French Léopold, from Old High German Leutpald, Liutbald, literally "bold among the people," from leudi, liut "people," from PIE root *leudh- (2) (see lede (n.2)) + bald "bold," from Proto-Germanic *baltha- (see bold (adj.))
leotard (n.): 1881, leotards, named for Jules Léotard (1830-1870), popular French trapeze artist, who performed in such a garment.
leper (n.): "one afflicted with leprosy," late 14c., earlier "the disease leprosy," from Late Latin lepra, from Greek lepra "leprosy," noun use of fem. of lepros (adj.) "scaly, scabby, rough, leprous," related to lepein "to peel," from lepos, lepis "a scale," from PIE root *lep- (1) "to peel," which also yields words for "something delicate and weak," via the notion of "small shaving, flake, scale" (cognates: Latin lepidus "pleasant, charming, fine, elegant, effeminate," lepos "pleasantness, agreeableness;" Old English læfer "rush, reed; metal plate;" Lithuanian lopas "patch, rag, cloth," lepus "soft, weak, effeminate").

Originally in Middle English this was the word for the disease itself (mid-13c., via Old French lepre); the shift in meaning to "person with leprosy" perhaps developed in Anglo-French, or is because the -er ending resembled an agent-noun affix. By mid-15c. other nouns for the disease were being coined (see leprosy). In English lepra also was an old name for psoriasis (late 14c.).
lepido-: before vowels lepid-, word-forming element used since late 18c. in science with a sense of "scale" (of a fish, etc.), comb. form of Greek lepis (genitive lepidos) "scale of a fish" (related to lepein "to peel;" see leper). As in lepidodendron (1819 in German), common fossil "club-moss tree" of the Carboniferous.
Lepidoptera (n.): order of insects with four scaly wings, 1773, the biological classification that includes butterflies and moths, coined 1735 in Modern Latin by Swedish botanist Carolus Linnaeus (Karl von Linné, 1707-1778) from lepido- "scale" + pteron "wing, feather" (see ptero-). Related: Lepidopteral; lepidopteran; lepidopterous.
lepidopterist (n.): "one who studies the Lepidoptera," 1826, from Lepidoptera + -ist. Related: Lepidopterology.
leprechaun (n.): c. 1600, from Irish lupracan, metathesis of Old Irish luchorpan literally "a very small body," from lu "little, small" (from PIE *legwh- "having little weight;" see lever (n.)) + corpan, diminutive of corp "body," from Latin corpus "body" (see corporeal).

Commonly spelled lubrican in 17c. English; "Century Dictionary" (1902) has it under leprechawn. Variant leithbragan probably is Irish folk etymology, from leith "half" + brog "brogue," because the spirit was "supposed to be always employed in making or mending a single shoe."
leprophilia (n.): "strong abnormal attraction to people with leprosy," 1959 (Graham Greene), from comb. form of leper (q.v.) + -philia. Related: Leprophil. Leprophobia is from 1888.
leprosy (n.): name given to various chronic skin diseases, later in more restricted use, 1530s, probably from leprous + -y (4). First used in Coverdale Bible, where it renders Hebrew cara'ath, which apparently was a comprehensive term for skin diseases. Because of pejorative associations, the use of the word in medical context has been banned by the World Health Organization and replaced by Hansen's disease (1938), named for Norwegian physician Gerhard Henrik Armauer Hansen (1841-1912) who in 1871 discovered the bacillus that causes it.

The Middle English name for the disease was leper (mid-13c.), from Old French liepre and Latin lepra (see leper). But as the sense of this shifted after late 14c. to mean "person with leprosy," English began coining new nouns for the disease: lepri, leprosity, lepruse all date from mid-15c. but are now obsolete. A place for their treatment is a leprosarium (1846) or leprosary (1869, from French).
leprous (adj.): "infected with leprosy," early 13c., leprus, from Old French lepros (Modern French lépreux), from Late Latin leprosus, from Latin lepra "leprosy" (see leper).
lepto-: word-forming element used from 19c. and meaning "fine, small, thin, delicate," from Greek leptos "small, slight, slender, delicate" (see lepton).
lepton (n.): elementary particle of small mass, 1948, from Greek leptos "small, slight, slender, delicate, subtle," literally "peeled," or "threshed out" (from lepein "to peel," from PIE *lep- (1), a root which yields words for "peel" as well as "small shaving, scale (of a fish)," hence used of things fine, delicate, or weak; see leper) + -on. In Greek it was the name of a small coin, from neuter of leptos. Related: Leptonic.
lere (v.): OE læran, Kentish leran "to teach" (cognate with Old Frisian lera, Old Saxon lerian, Dutch leeren, Old High German leran, German lehren "to teach"), literally "to make known;" see lore). From early 13c. as "to learn."
Lernaean: also Lernean, from Latin Lernaeus, from Greek Lernaios, from Lerne, name of a marshy district and lake in Argolis, home of the Lernaean hydra.
lesbian (adj.): 1590s, "pertaining to the island of Lesbos," from Latin Lesbius, from Greek lesbios "of Lesbos," Greek island in northeastern Aegean Sea (the name originally may have meant "wooded"), home of Sappho, great lyric poet whose erotic and romantic verse embraced women as well as men, hence meaning "relating to homosexual relations between women, characterized by erotic interest in other women" (1890; the noun lesbianism from this sense is attested from 1870) and the noun, which is first recorded 1925.

Sappho's particular association with erotic love between women dates to at least 1825 in writing in English, though lesbian and other the modern words formed from it are later. Before this, the principal figurative use of Lesbian was lesbian rule (c. 1600 and especially common in 17c.) a mason's rule of lead, of a type used in ancient times on Lesbos, which could be bent to fit the curves of a molding; hence, figuratively, "pliant morality or judgment."
And this is the nature of the equitable, a correction of law where it is defective owing to its universality. ... For when the thing is indefinite the rule also is indefinite, like the leaden rule used in making the Lesbian moulding; the rule adapts itself to the shape of the stone and is not rigid, and so too the decree is adapted to the facts. [Aristotle, "Nicomachean Ethics"]
It also was used in English from 1775 in reference to wines from Lesbos. Though the specific "pertaining to female homosexuality" is recent, Lesbian had long before that a suggestion of "amatory, erotic," "From the reputed character of the inhabitants and the tone of their poetry" [Century Dictionary]. The island's erotic reputation was ancient; Greek had a verb lesbiazein "to imitate the Lesbians," which implied "sexual initiative and shamelessness" among women (especially fellatio), but not necessarily female homosexuality, and they did not differentiate such things the way we have.
lesbian (n.): 1925, "female homosexual," from lesbian (adj.).
lesbianism (n.): 1870, from lesbian (adj.) + -ism. See also tribadism.
lesbo: by 1940, colloquial shortening of lesbian.
lese-majesty (n.): "offense against sovereign authority, treason," 1530s (mid-15c. as an Anglo-French word), from French lèse-majesté (15c.), from Latin laesa majestos "violated majesty," from laesus, past participle of laedere "to hurt, injure, damage, offend, insult," a word of unknown origin. Brachet calls French lèse "a latinism introduced by the lawyers."