lief (adj.) Look up lief at Dictionary.com
Old English leof "dear, valued, beloved, pleasant;" also as a noun, "a beloved person, friend," from Proto-Germanic *leubo- (source also of Old Norse ljutr, Old Frisian liaf, Dutch lief, Old High German liob, German lieb, Gothic liufs "dear, beloved"), from PIE root *leubh- "love" (see love (n.)). As an adverb, "dearly, willingly" from c. 1250. I want and I'd love to are overworked and misused to fill the hole left in the language when I would lief faded in 17c.
liege (adj.) Look up liege at Dictionary.com
word used by a vassal to address his superior or lord in the feudal system, c. 1300, from Anglo-French lige (late 13c.), Old French lige "(feudal) liege, free, giving or receiving fidelity," perhaps from Late Latin laeticus "cultivated by serfs," from laetus "serf," which probably is from Proto-Germanic *lethiga- "freed" (source also of Old English læt "half-freedman, serf;" Old High German laz, Old Frisian lethar "freedman"), from PIE root *le- "let go, slacken" (see let (v.)). Or the Middle English word may be directly from Old High German leidig "free." As a noun from late 14c., both as "vassal" and "lord." Hence, liege-man "a vassal sworn to the service and support of a lord, who in turn is obliged to protect him" (mid-14c.).
lien (n.) Look up lien at Dictionary.com
"right to hold property of another until debt is paid," 1530s, from Middle French lien "a band or tie," from Latin ligamen "bond," from ligare "to bind, tie" (see ligament).
lieno- Look up lieno- at Dictionary.com
word-forming element meaning "spleen," from Latin lien "spleen" (see spleen).
lier (n.) Look up lier at Dictionary.com
"one who reclines;" 1580s, agent noun from lie (v.2).
lieu Look up lieu at Dictionary.com
late 13c., from Old French lieu "place, position, situation, rank," from Latin locum (nominative locus) "place."
lieutenancy (n.) Look up lieutenancy at Dictionary.com
mid-15c., from lieutenant + -cy.
lieutenant (n.) Look up lieutenant at Dictionary.com
late 14c., "one who takes the place of another," from Old French lieu tenant "substitute, deputy," literally "placeholder," from lieu "place" (see lieu) + tenant, present participle of tenir "to hold" (see tenant). The notion is of a "substitute" for higher authority. Specific military sense of "officer next in rank to a captain" is from 1570s. Pronunciation with lef- is common in Britain, and spellings to reflect it date back to 14c., but the origin of this is a mystery (OED rejects suggestion that it comes from old confusion of -u- and -v-).
life (n.) Look up life at Dictionary.com
Old English life (dative lif) "existence, lifetime, way of life, condition of being a living thing, opposite of death," from Proto-Germanic *libam (source also of Old Norse lif "life, body," Dutch lijf "body," Old High German lib "life," German Leib "body"), properly "continuance, perseverance," from PIE *leip- "to remain, persevere, continue; stick, adhere" (see leave (v.)). Much of the modern range of meanings was present in Old English. Meaning "property which distinguishes living from non-living matter" is from 1560s. Sense of "vitality, energy" is from 1580s. Extended 1703 to "term of duration (of inanimate objects)."

Life-jacket is from 1840; life-preserver from 1630s of anything that is meant to save a life, 1803 of devices worn to prevent drowning. Life-saver is from 1883, figurative use from 1909, as a brand of hard sugar candy, from 1912, so called for shape. Life-form is from 1861. Life cycle is from 1855.
life of Riley (n.) Look up life of Riley at Dictionary.com
"life at ease," expression popularized by 1917, American English, sometimes said to trace to various songs from c. 1902.
life-boat Look up life-boat at Dictionary.com
also lifeboat, 1801 (the thing itself attested by 1785), from life (n.) + boat.
life-size (adj.) Look up life-size at Dictionary.com
1820, from life (n.) + size (n.).
lifeblood (n.) Look up lifeblood at Dictionary.com
also life-blood, 1580s, "blood necessary for life," from life (n.) + blood (n.). Figurative and transferred use is from 1590s.
lifeguard (n.) Look up lifeguard at Dictionary.com
also life-guard, 1640s, "bodyguard of soldiers," from life (n.) + guard (n.), translating German leibgarde. Sense of "person paid to watch over bathers" is by 1896.
lifeless (adj.) Look up lifeless at Dictionary.com
Old English lifleas "inanimate, dead;" see life + -less. Meaning "with no living things" is from 1728. Related: Lifelessly; lifelessness.
lifelike (adj.) Look up lifelike at Dictionary.com
1610s, "likely to live," from life (n.) + like (adj.). Meaning "exactly like the living original" is from 1725.
lifeline (n.) Look up lifeline at Dictionary.com
also life-line, 1700, "rope used somehow to save lives," from life (n.) + line (n.); figurative sense first attested 1860. Sense in palmistry from 1890.
lifelong (adj.) Look up lifelong at Dictionary.com
also life-long, "continuing a lifetime," 1855, from life (n.) + long (adj.).
lifer (n.) Look up lifer at Dictionary.com
"prisoner serving a life sentence," 1830, from life (n.).
lifespan (n.) Look up lifespan at Dictionary.com
also life span, 1918, from life (n.) + span (n.1).
lifestyle (n.) Look up lifestyle at Dictionary.com
also life-style, 1929, from life (n.) + style (n.); originally a specific term used by Austrian psychologist Alfred Adler (1870-1937); broader sense is by 1961.
lifetime (n.) Look up lifetime at Dictionary.com
also life-time, early 13c., from life (n.) + time (n.). One word from 19c. Old English had lifdæg in same sense, literally "life day."
lifeway (n.) Look up lifeway at Dictionary.com
"way of life," 1960s, an unconscious revival of Old English lifweg; see life (n.) + way (n.).
lift (v.) Look up lift at Dictionary.com
c. 1200, from Old Norse lypta "to raise," from Proto-Germanic *luftijan (source also of Middle Low German lüchten, Dutch lichten, German lüften "to lift;" Old English lyft "heaven, air," see loft). The meaning "steal" (as in shop-lift) is first recorded 1520s. Related: Lifted; lifting.
lift (n.) Look up lift at Dictionary.com
late 15c., "act of lifting," from lift (v.). Meaning "act of helping" is 1630s; that of "cheering influence" is from 1861. Sense of "elevator" is from 1851; that of "upward force of an aircraft" is from 1902. Meaning "help given to a pedestrian by taking him into a vehicle" is from 1712.
liftoff (n.) Look up liftoff at Dictionary.com
also lift-off, "vertical take-off of a rocket, etc.," 1956, American English, from lift (v.) + off.
ligament (n.) Look up ligament at Dictionary.com
late 14c., from Latin ligamentum "band, tie, ligature," from ligare "to bind, tie," from PIE *leig- "to bind" (source also of Albanian lith "I bind," Middle Low German lik "band," Middle High German geleich "joint, limb"). Related: Ligamental; ligamentary.
ligand (n.) Look up ligand at Dictionary.com
1952, from Latin ligandus, gerundive of ligare "to bind" (see ligament).
ligate (v.) Look up ligate at Dictionary.com
1590s, from Latin ligatus, past participle of ligare "to bind" (see ligament). Related: Ligated; ligating.
ligation (n.) Look up ligation at Dictionary.com
1590s, from Middle French ligation, from Late Latin ligationem (nominative ligatio), noun of action from past participle stem of ligare "to bind" (see ligament).
ligature (n.) Look up ligature at Dictionary.com
c. 1400, "something used in tying or binding," from Middle French ligature (14c.), from Late Latin ligatura "a band," from Latin ligatus, past participle of ligare "to bind" (see ligament). In musical notation from 1590s; of letters joined in printing or writing from 1690s.
light (n.) Look up light at Dictionary.com
"brightness, radiant energy," Old English leht, earlier leoht "light, daylight," from Proto-Germanic *leukhtam (source also of Old Saxon lioht, Old Frisian liacht, Middle Dutch lucht, Dutch licht, Old High German lioht, German Licht, Gothic liuhaþ "light"), from PIE *leuk- "light, brightness" (source also of Sanskrit rocate "shines;" Armenian lois "light," lusin "moon;" Greek leukos "bright, shining, white;" Latin lucere "to shine," lux "light," lucidus "clear;" Old Church Slavonic luci "light;" Lithuanian laukas "pale;" Welsh llug "gleam, glimmer;" Old Irish loche "lightning," luchair "brightness;" Hittite lukezi "is bright").

The -gh- was an Anglo-French scribal attempt to render the Germanic hard -h- sound, which has since disappeared from this word. The figurative spiritual sense was in Old English; the sense of "mental illumination" is first recorded mid-15c. Meaning "something used for igniting" is from 1680s. Meaning "a consideration which puts something in a certain view (as in in light of) is from 1680s. Something that's a joy and a delight has been the light of (someone's) eyes since Old English:
Ðu eart dohtor min, minra eagna leoht [Juliana].
To see the light "come into the world" is from 1680s; later in a Christian sense.
light (adj.1) Look up light at Dictionary.com
"not heavy," from Old English leoht "not heavy, light in weight; easy, trifling; quick, agile," from Proto-Germanic *lingkhtaz (source also of Old Norse lettr, Swedish lätt, Old Frisian, Middle Dutch licht, German leicht, Gothic leihts), from PIE root *legwh- "not heavy, having little weight" (source also of Latin levis "light," Old Irish lu "small;" see lever).

The notion in make light of (1520s) is of "unimportance." Alternative spelling lite, the darling of advertisers, is first recorded 1962. The adverb is Old English leohte, from the adjective. Light-skirts "woman of easy virtue" is attested from 1590s. To make light of is from 1520s.
light (v.1) Look up light at Dictionary.com
"touch down," from Old English lihtan "to alight; alleviate, leave," from Proto-Germanic *linkhtijan, literally "to make light," from *lingkhtaz "not heavy" (see light (adj.1)). Apparently the ground sense is "to dismount a horse, etc., and thus relieve it of one's weight." To light out "leave hastily" is 1870, from a nautical meaning "move out, move heavy objects," of unknown origin but perhaps belonging to this word (compare lighter (n.1)).
light (v.2) Look up light at Dictionary.com
"to shed light; to set on fire," late Old English lihtan (Anglian), liehtan (West Saxon), originally transitive, "to ingite, set on fire," also in a spiritual sense, "to illuminate, fill with brightness." It is common Germanic (cognates: Old Saxon liohtian, Old High German liuhtan, German leuchten, Gothic liuhtjan "to light"), from the source of light (n.).

Meaning "to shed light, illuminate," also "to furnish light for" are from c. 1200; sense of "emit light, shine" is from c. 1300. Buck writes that light is "much more common than kindle even with fire, and only light, not kindle, with candle, lamp, pipe, etc." Related: Lighted; lighting.
light (adj.2) Look up light at Dictionary.com
"not dark," Old English leoht, common Germanic (cognates: Old Saxon and Old High German lioht, Old Frisian liacht, German licht "bright," from the source of Old English leoht (see light (n.)). Meaning "pale-hued" is from 1540s.
light bulb (n.) Look up light bulb at Dictionary.com
also lightbulb, 1884, from light (n.) + bulb.
light year (n.) Look up light year at Dictionary.com
also light-year, lightyear, "distance light travels in one year," 1888, from light (n.) + year.
light-fingered (adj.) Look up light-fingered at Dictionary.com
"thievish," 1540s, from light (adj.1) + finger.
light-headed (adj.) Look up light-headed at Dictionary.com
also lightheaded, "dizzy," 1530s; from light (adj.1) + head (n.). Related: Light-headedness.
light-hearted (adj.) Look up light-hearted at Dictionary.com
also lighthearted, "cheerful," c. 1400, from light (adj.1) + hearted. Related: Light-heartedly; light-heartedness.
lighten (v.1) Look up lighten at Dictionary.com
"to make less heavy," figuratively "to make cheerful," mid-14c., from light (adj.1) + -en (1). Related: Lightened; lightening.
lighten (v.2) Look up lighten at Dictionary.com
"shed light upon, illuminate, brighten," early 14c., from light (n.) -en (1). Meaning "to grow brighter" is late 14c. Of faces, expressions, etc., from 1795. Related: Lightened; lightening.
lightening (n.) Look up lightening at Dictionary.com
"the shedding of light," mid-14c., verbal noun from lighten (v.2). Meaning "alleviation of weight" (literal and figurative) is from 1520s, from lighten (v.1).
lighter (n.1) Look up lighter at Dictionary.com
"barge," late 15c., agent noun from light (adj.1), with a sense of lightening a load, or else from Dutch lichter, from lichten "to lighten, unload," on the same notion. They are used in loading or unloading ships that cannot approach a wharf.
lighter (n.2) Look up lighter at Dictionary.com
"person who lights," 1550s, agent noun from light (v.2).
lighthouse (n.) Look up lighthouse at Dictionary.com
1620s, from light (n.) + house (n.).
lighting (n.) Look up lighting at Dictionary.com
"shining, illumination," Old English lihting, from leoht (see light (n.)).
lightless (adj.) Look up lightless at Dictionary.com
Old English leohtleas; see light (n.) + -less.
lightly (adv.) Look up lightly at Dictionary.com
Old English leohtlice "so as not to be heavy" (of material things, but also of sleep, blows, etc.); cognate with Old Frisian lichtelik, Old High German lihtlihho, German leichtlich, Old Norse lettlega (see light (adj.1)). Meaning "frivolously, indifferently" is from early 13c.