Online Etymology Dictionary

legged: "having legs" (of a specified kind), usually in compounds, mid-15c., from leg (n.).
legging (n.): "extra outer covering to protect the leg," 1763, from leg (n.). Related: Leggings.
leggy (adj.): 1787, "having notably long legs," from leg (n.) + -y (2). At first with suggestion of disproportion and ungainliness; attested by 1866 approvingly. Related: Legginess.
Leghorn: city in Italy (modern Livorno, in 16c.-17c. Legorno), from Latin Liburnus, from the native people name Liburni, which is of unknown signification. Spanish Liorna, French Livourne. As a breed of fowl, 1869.
legibility (n.): 1670s; see legible + -ity.
legible (adj.): late 14c., from Late Latin legibilis "that can be read, written plainly," from Latin legere "to read" (see lecture (n.)). Related: Legibly.
legicide (n.): "a destroyer of laws," 1680s, from Latin legis, genitive of lex "law" (see legal (adj.)) + -cide.
legion (n.): c. 1200, "a Roman legion," from Old French legion "squad, band, company, Roman legion" from Latin legionem (nominative legio) "Roman legion, body of soldiers, a levy of troops," from legere "to gather; to choose, pick out, select" (also "to read;" see lecture (n.)). Tucker writes that "The common sense is 'pick,'" but it is unclear whether the use here is "picking up or picking out." Roughly 3,000 to 6,000 men, under Marius usually with attached cavalry. "The legions were numbered in the order of their levy, but were often known by particular names" [Lewis].
The great power of the Roman legion was due to its rigid discipline and its tactical formation in battle, which was so open and flexible as to enable it to meet every emergency without surprise or derangement.
Generalized sense of "a large number of persons" (c. 1300) is due to translations of the allusive phrase in Mark v:9. Of modern military bodies from 1590s. American Legion, U.S. association of ex-servicemen, founded in 1919. Legion of Honor is French légion d'honneur, an order of distinction founded by Napoleon in 1802. Foreign Legion is French légion étrangère "body of foreign volunteers in a modern army," originally Polish, Belgian, etc. units in French army; they traditionally served in colonies or distant expeditions. Related: Legionary.
legionnaire (n.): 1818, from French légionnaire, from légion (see legion). Legionnaires' Disease, caused by Legionella pneumophilia, was named after the lethal outbreak of July 1976 at the American Legion convention in Philadelphia's Bellevue Stratford Hotel. Hence also Legionella as the name of the bacterium.
legislate (v.): "to make laws," 1805, back-formation from legislation or legislator. Related: Legislated; legislating.
legislation (n.): 1650s, "the enacting of laws," from French législation (14c.), from Late Latin legislationem (nominative legislatio), properly two words, legis latio, "a proposing (literally 'bearing') of a law;" see legislator. Meaning "the product of legislative action" is from 1838.
legislative (adj.): 1640s; from legislator + -ive. Related: Legislatively.
legislator (n.): "a lawgiver, a maker of laws," c. 1600, from Latin legis lator "proposer of a law," from legis, genitive of lex "law" (see legal (adj.)) + lator "proposer," agent noun of latus "borne, brought, carried" (see oblate (n.)), which was used as past tense of ferre "to carry" (see infer). In U.S., generally a member of a state, territorial, or colonial legislature. Fem. form legislatrix is from 1670s; legislatress from 1711. Related: Legislatorial.
legislature (n.): "a body of lawmakers," 1670s; see legislator + -ure.
legit (adj.): colloquial shortening of legitimate (adj.), 1897, originally in theater, in reference to legitimate drama, that which has literary merit (Shakespeare, etc., etc.).
legitimacy (n.): "state of being legitimate" in any sense, 1690s of children, 1812 of kings and governments, general use by 1836; see legitimate (adj.) + -cy. Legitimateness (1610s) is an earlier word for it. Middle English had legitimation (mid-15c.).
legitimate (adj.): mid-15c., "lawfully begotten, born of parents legally married," from Middle French legitimer and directly from Medieval Latin legitimatus, past participle of legitimare "make lawful, declare to be lawful," from Latin legitimus "lawful," originally "fixed by law, in line with the law," from lex (genitive legis) "law" (see legal). Transferred sense of "genuine, real" is attested from 1550s. Related: Legitimately; legitimateness. The older adjective in English was legitime "lawful, of legitimate birth" (late 14c.), from Old French legitime, from Latin legitimus.
legitimate (v.): "establish the legitimacy of, make lawful," 1590s, from Medieval Latin legitimatus, past participle of legitimare "make lawful" (see legitimate (adj.)). Related: Legitimated; legitimating.
legitimation (n.): mid-15c., from Middle French légitimation, from Medieval Latin legitimationem (nominative legitimatio), noun of action from past participle stem of legitimare "make lawful, declare to be lawful" (see legitimate (adj.)).
legitimism (n.): "insistence upon legitimacy," 1849, from French légitimisme (1834); see legitimate (adj.) + -ism. In 19c. especially with reference to French or Spanish politics and conservative adherence to "legitimate" claimants to the throne.
legitimist (n.): 1841, from French légitimiste (1830), from légitime "legitimate," from legitimer (see legitimate (adj.)). A supporter of "legitimate" authority, in France, after 1830, especially of supporters of the elder Bourbon line (in opposition to that of the Orleans family).
legitimize (v.): 1795, from Latin legitimus "lawful" (see legitimate (adj.)) + -ize. Earlier were legitimatize (1791), legitimate (1590s). Related: Legitimized; legitimizing; legitimization.
legless (adj.): 1590s, from leg (n.) + -less. Related: Leglessly; leglessness.
Lego: 1954, proprietary name (in use since 1934, according to the company), from Danish phrase leg godt "play well." The founder, Danish businessman Ole Kirk Christiansen (1891-1958), didn't realize until later that the word meant "I study" or "I put together" in Latin.
legume (n.): plant of the group of the pulse family, pea, 1670s, from French légume (16c.), from Latin legumen "pulse, leguminous plant," of unknown origin. One suggestion ties it to Latin legere "to gather" (see lecture (n.)), because they can be scooped by the handful. Middle English had the word in the Latin form legumen (late 14c.).
leguminous (adj.): early 15c., from Latin legumen (see legume) + -ous.
Lehrjahre (n.): 1865, from German Lehrjahre, from lehren "to learn" (see learn) + Jahre "years" (see year (n.)).
lei (n.): 1843, from Hawaiian, "ornament worn about the neck or head."
Leibnitz: Gottfried Wilhelm Leibnitz (also Leibniz), 1646-1716, German philosopher and mathematician, independent inventor (Newton was the other) of differential and integral calculus.
Leica: 1925, proprietary name of cameras made by firm of Ernst & Leitz Gesellschaft, Wetzlar, Germany. From Leitz + ca(mera).
Leicester: Middle English, earlier Ligraceaster, Ligera ceaster (early 10c.) "Roman Town of the People Called Ligore," a tribal name, perhaps "dwellers by the River Ligor." For second element, see Chester. The site is the Roman Ratae Coritanorum, fortified tribal capital of the Coritani, whose name is of unknown origin, with a Celtic word for "ramparts." The modern name "is best regarded as a new descriptive term for a deserted site" [Watts, "Cambridge Dictionary of English Place-Names"].
Leighton: place name (and surname), Old English leahtun, from earlier *leactun "a garden," from leac (see leek) + tun "farm, settlement, enclosure" (see town (n.)).
Leila: fem. proper name, from Arabic Laylah, from laylah "night."
leio-: scientific word-forming element meaning "smooth," from Greek leios "smooth, level, flat; plain, unembroidered; beardless." E.g. leiotrichy, in ethnology, of races, "condition of having straight, lank hair" (1924).
leisure (adj.): "free from business, idle, unoccupied," 1660s, from leisure (n.).
leisure (n.): c. 1300, leisir, "free time, time at one's disposal," also (early 14c.) "opportunity to do something, chance, occasion, an opportune time," also "lack of hurry," from Old French leisir, variant of loisir "capacity, ability, freedom (to do something); permission; spare time; free will; idleness, inactivity," noun use of infinitive leisir "be permitted," from Latin licere "to be allowed" (see licence (n.)).

Especially "opportunity afforded by freedom from necessary occupations" (late 14c.). "In Fr. the word has undergone much the same development of sense as in Eng." [OED]. The -u- appeared 16c., probably on analogy of pleasure (n.), etc. To do something at leisure "without haste, with deliberation" (late 14c.) preserves the older sense. To do something at (one's) leisure "when one has time" is from mid-15c.
leisured (adj.): of persons, "having ample leisure, not occupied with business," 1794, from leisure (n.). A verb leisure is not attested until 20c. and is rare. Phrase leisured class attested by 1836.
leisurely (adj.): c. 1600, from leisure (n.) + -ly (1). Earlier adjectives were leisurable (1530s), leisureful (mid-15c.). Related: Leisureliness.
leisurely (adv.): late 15c., "not hastily, deliberately," from leisure (n.) + -ly (2).
leitmotif (n.): also leitmotiv, "a musical figure to which some definite meaning is attached," 1876, from German Leitmotiv, literally "leading motive," from leiten "to lead" (see lead (v.1)) + Motiv (see motive). A term associated with Wagnerian musical drama, though the thing itself is at least as old as Mozart. "The leitmotif must be characteristic of the person or thing it is intended to represent." ["Elson's Music Dictionary"]
lek (v.): of certain animals, "to engage in courtship displays," 1871, probably from Swedish leka "to play," cognate of English dialectal verb lake (see lark (n.2)). Related: Lekking.
LEM (n.): acronym (initialism) for lunar excursion module, 1962, from the U.S. space program.
leman (n.): "sweetheart, paramour, loved one" (archaic), c. 1200, lemman, "loved one of the opposite sex; paramour, lover; wife;" also "a spiritually beloved one; redeemed soul, believer in Christ; female saint devoted to chastity; God, Christ, the Virgin Mary;" also a term of intimate address to a friend or lover, contracted from late Old English leofman, a compound of leof "dear" (see lief) + man "human being, person" (see man (n.)).

Originally of either gender, though in deliberate archaic usage it tends to be limited to women. Often in religious use in early Middle English, of brides of Christ, the spiritually beloved of God, etc.; by c. 1300 it could mean "betrothed lover," and by late 14c. it had the pejorative sense "concubine, mistress, gallant." For loss of medial -f-, compare had.
lemma (n.): 1560s, in mathematics, from Greek lemma (plural lemmata) "something received or taken; an argument; something taken for granted," from root of lambanein "to take" (see analemma). Related: Lemmatical.
lemming (n.): small arctic rodent, c. 1600, from Norwegian lemming, from Old Norse lomundr "lemming." Perhaps from Lapp luomek. Figurative sense (in reference to their prolific breeding and sudden mass migrations that sometimes end in plunges into the sea) is from 1958.
lemniscus (n.): 1811, from Late Latin lemniscus "a pendent ribbon," from Greek lemniskos "woolen ribbon," perhaps originally or literally "of Lemnos," the island in the Aegean, but if so the reason is obscure. Related: Lemniscate (adj.), 1781.
Lemnos: Greek island, the name is believed to be of Phoenician origin, from Semitic root l-b-n "white." Related: Lemnian.
lemon (n.1): type of ovate, pale yellow citrus fruit, c. 1400, lymon, from Old French limon "citrus fruit" (12c.), which comes via Provençal or Italian from Arabic laimun, from Persian limu(n), a generic terms for citrus fruits (compare lime (n.2)). Cognate with Sanskrit nimbu "the lime."

Meaning "person with a tart disposition" is from 1863. For the sense "worthless thing," see lemon (n.2). Slang meaning "a Quaalude" is 1960s, from Lemmon, name of a pharmaceutical company that once manufactured the drug. The surname is from Middle English leman "sweetheart, lover." Lemon-juice is attested from 1610s; the candy lemon-drop from 1807. The East Indian lemon-grass (1837) is so called for its smell.
lemon (n.2): "worthless thing, disappointment, booby prize," 1909, American English slang; from lemon (n.1), perhaps via a criminal slang sense of "a person who is a loser, a simpleton," perhaps an image of someone a sharper can "suck the juice out of." A pool hall hustle was called a lemon game (1908); while to hand someone a lemon was British slang (1906) for "to pass off a sub-standard article as a good one." Or it simply may be a metaphor for something which leaves a bad taste in one's mouth. Specific sense of "second-hand car in poor condition" is by 1931.
lemon (v.): 1767 (implied in lemoned), from lemon (n.1).