lock-up (n.) Look up lock-up at Dictionary.com
"detention cell for offenders," 1838, perhaps short for earlier lock-up house; from lock (v.) + up. Meaning "action of locking up" is from 1845. The verbal phrase lock up is recorded from early 15c.
lockable (adj.) Look up lockable at Dictionary.com
1832, from lock (v.) + -able. Related: Lockability.
lockdown (n.) Look up lockdown at Dictionary.com
also lock-down, from 1940s in various mechanical senses, from lock (v.) + down (adv.). Prison sense is by 1975, American English.
locker (n.) Look up locker at Dictionary.com
small chest that can be locked, late 14c., agent noun from Middle English lokken (see lock (v.)). Earlier "a mechanism for locking" (early 14c.).
locket (n.) Look up locket at Dictionary.com
mid-14c., "iron cross-bar of a window," from Old French loquet "door-handle, bolt, latch," diminutive of loc "lock, latch," from Frankish or some other Germanic source (compare Old Norse lok "fastening, lock;" see lock (n.1)). Meaning "ornamental case with hinged cover" (containing a lock of hair, miniature portrait, etc.) first recorded 1670s.
lockout (n.) Look up lockout at Dictionary.com
also lock-out, "act of locking out workers," 1854, from lock (v.) + out.
locksmith (n.) Look up locksmith at Dictionary.com
early 13c., from lock (n.1) + smith.
loco (adj.) Look up loco at Dictionary.com
1844, American English, from Spanish loco (adj.) "insane," of uncertain origin, perhaps from Arabic lauqa, fem. of 'alwaq "fool, crazy person." Loco-weed (1877) was name given to species of western U.S. plants that cause cattle and horse diseases that make them stagger and act strangely.
loco- Look up loco- at Dictionary.com
word-forming element meaning "from place to place," from comb. form of Latin locus (see locus).
loco-foco (n.) Look up loco-foco at Dictionary.com
"self-igniting cigar or match," 1839 (but presumably older), American English, of unknown origin, perhaps from a misapprehension of the meaning of the first element of locomotive as "self-" + Spanish fuego "fire." During one heated political meeting in N.Y., the lights went out and the delegates used such matches to relight them, thence the name loco-foco entered U.S. political jargon (1837), usually applied to a radical faction of the Democratic Party, but by the Whigs applied to all Democrats.
locomote (v.) Look up locomote at Dictionary.com
1831, back-formation from locomotion.
locomotion (n.) Look up locomotion at Dictionary.com
1640s, formed in English from Latin loco "from a place" (ablative of locus "place") + motionem (nominative motio) "motion, a moving."
locomotive (adj.) Look up locomotive at Dictionary.com
1610s, "pertaining to movement," from French locomotif, from Latin loco "from a place" (ablative of locus "place;" see locus) + Late Latin motivus "moving" (see motive). The noun meaning "railroad engine" is from 1829, short for locomotive engine (1814).
locomotor (adj.) Look up locomotor at Dictionary.com
1822, from Latin loco "from a place" (ablative of locus "place") + motor.
locum tenens (n.) Look up locum tenens at Dictionary.com
Medieval Latin, "one who holds the place (of another);" from locum (nominative locus; see locus) + tenens, present participle of tenere (see tenant).
locus (n.) Look up locus at Dictionary.com
(plural loci), 1715, "locality," from Latin locus "a place, spot, position," from Old Latin stlocus, literally "where something is placed," from PIE root *st(h)el- "to cause to stand, to place." Used by Latin writers for Greek topos. Mathematical sense by 1750.
locust (n.1) Look up locust at Dictionary.com
"grasshopper," early 14c., borrowed earlier in Old French form languste (c. 1200), from Latin locusta "locust, lobster" (see lobster).
In the Hebrew Bible there are nine different names for the insect or for particular species or varieties; in the English Bible they are rendered sometimes 'locust,' sometimes 'beetle,' 'grasshopper,' 'caterpillar,' 'palmerworm,' etc. The precise application of several names is unknown. [OED]
locust (n.2) Look up locust at Dictionary.com
North American tree, 1630s, originally "carob tree" (1610s), whose fruit supposedly resembled the insect (see locust (n.1)). Greek akris "locust" often was applied in the Levant to carob pods. Soon applied in English to other trees as well.
locution (n.) Look up locution at Dictionary.com
"style of speech," early 15c., from Latin locutionem (nominative locutio) "a speaking, speech, discourse; way of speaking," noun of action from past participle stem of loqui "to speak," from PIE root *tolk(w)- (source also of Old Irish ad-tluch- "to thank," to-tluch- "to ask;" Old Church Slavonic tloko "interpretation, explanation"). Related: Locutionary.
lode (n.) Look up lode at Dictionary.com
original Middle English spelling of load (n.), and custodian of most of the original meaning of "way, course, carrying." Differentiation in sense took place 16c. Mining sense of "vein of metal ore" is from c. 1600, from notion of miners "following" it through the rock.
loden (n.) Look up loden at Dictionary.com
"coarse woolen cloth," 1880, from German loden "thick woolen cloth."
lodestar (n.) Look up lodestar at Dictionary.com
late 14c. (late 13c. as a surname), an old name for the pole star (compare Old Norse leiðarstjarna) as the star that "leads the way" in navigation; from lode (n.) + star (n.). Figurative use from late 14c.
lodestone (n.) Look up lodestone at Dictionary.com
"magnetically polarized oxide of iron," 1510s, literally "way-stone," from lode + stone (n.). So called because it was used to make compass magnets to guide mariners. Figurative use from 1570s.
lodge (n.) Look up lodge at Dictionary.com
mid-13c. in surnames and place names; late 13c. as "small building or hut," from Old French loge "arbor, covered walk; hut, cabin, grandstand at a tournament," from Frankish *laubja "shelter" (cognate with Old High German louba "porch, gallery," German Laube "bower, arbor"), from Proto-Germanic *laubja- "shelter," likely originally "shelter of foliage," or "roof made from bark," from root of leaf (n.).

"Hunter's cabin" sense is first recorded late 14c. Sense of "local branch of a society" is first recorded 1680s, from mid-14c. logge "workshop of masons." Also used of certain American Indian buildings, hence lodge-pole (1805). Feste of Logges (c. 1400) was a Middle English rendition of the Old Testament Jewish Feast of Tabernacles.
lodge (v.) Look up lodge at Dictionary.com
c. 1200, loggen, "to encamp, set up camp;" c. 1300 "to put in a certain place," from Old French logier "lodge; find lodging for" (Modern French loger), from loge (see lodge (n.)). From late 14c. as "to dwell, live; to have temporary accomodations; to provide (someone) with sleeping quarters; to get lodgings." Sense of "to get a thing in the intended place, to make something stick" is from 1610s. Related: Lodged; lodging.
lodgement (n.) Look up lodgement at Dictionary.com
1590s, from French logement (14c.) "accommodation, lodgings," from Old French logier (see lodge (v.)).
lodger (n.) Look up lodger at Dictionary.com
early 14c., originally "tent-dweller," agent noun from lodge (v.). From c. 1200 as a surname. Meaning "one who lives in rented rooms" is from 1590s.
lodging (n.) Look up lodging at Dictionary.com
early 14c., "encampment;" late 14c., "temporary accommodation; place of residence," verbal noun from lodge (v.). Related: Lodgings.
loess (n.) Look up loess at Dictionary.com
1833 (in Lyell), "unstratified deposit of loam," coined 1823 by German mineralogist Karl Cäsar von Leonhard (1779-1862) from German Löss "yellowish-gray soil," from Swiss German lösch (adj.) "loose" (compare German los; see loose (adj.)). Related: Loessial.
loft (n.) Look up loft at Dictionary.com
"an upper chamber," c. 1300, from late Old English loft "the sky; the sphere of the air," from Old Norse lopt "air, sky," originally "upper story, loft, attic" (Scandinavian -pt- pronounced like -ft-), from Proto-Germanic *luftuz "air, sky" (source also of Old English lyft, Dutch lucht, Old High German luft, German Luft, Gothic luftus "air").

Sense development is from "loft, ceiling" to "sky, air." Buck suggests ultimate connection with Old High German louft "bark," louba "roof, attic," etc., with development from "bark" to "roof made of bark" to "ceiling," though this did not directly inform the meaning "air, sky." But Watkins says this is "probably a separate Germanic root." Meaning "gallery in a church" first attested c. 1500.
loft (v.) Look up loft at Dictionary.com
"to hit a ball high in the air," 1856, originally in golf, from loft (n.). Related: Lofted; lofting. An earlier sense was "to put a loft on" (a building), 1560s; also "to store (goods) in a loft" (1510s).
lofty (adj.) Look up lofty at Dictionary.com
"exalted, of high rank," early 15c.; also "with a high purpose," from loft + -y (2). From early 14c. as a surname. Literal sense of "high" is attested from 1580s. Related: Loftily; loftiness.
log (n.1) Look up log at Dictionary.com
unshaped large piece of tree, early 14c., of unknown origin. Old Norse had lag "felled tree" (from stem of liggja "to lie"), but on phonological grounds many etymologists deny that this is the root of English log. Instead, they suggest an independent formation meant to "express the notion of something massive by a word of appropriate sound." OED compares clog (n.) in its original Middle English sense "lump of wood." Log cabin (1770) in American English has been a figure of the honest pioneer since the 1840 presidential campaign of William Henry Harrison. Falling off a log as a type of something easy to do is from 1839.
log (v.2) Look up log at Dictionary.com
"to enter into a log-book," 1823, from log (n.2). Meaning "to attain (a speed) as noted in a log" is recorded by 1883. Related: Logged; logging.
log (n.2) Look up log at Dictionary.com
"record of observations, readings, etc.," 1842, sailor's shortening of log-book "daily record of a ship's speed, progress, etc." (1670s), from log (n.1). The book so called because a wooden float at the end of a line was cast out to measure a ship's speed. General sense by 1913.
log (v.1) Look up log at Dictionary.com
"to fell a tree," 1717; earlier "to strip a tree" (1690s), from log (n.1). Related: Logged; logging.
log in (v.) Look up log in at Dictionary.com
1963 in the computing sense, from log (v.2) + in (adv.).
loganberry (n.) Look up loganberry at Dictionary.com
1893, American English, named for U.S. horticulturalist James H. Logan (1841-1928), who developed it by crossing a blackberry and a raspberry.
logarithm (n.) Look up logarithm at Dictionary.com
1610s, Modern Latin logarithmus, coined by Scottish mathematician John Napier (1550-1617), literally "ratio-number," from Greek logos "proportion, ratio, word" (see logos) + arithmos "number" (see arithmetic).
logarithmic (adj.) Look up logarithmic at Dictionary.com
1690s, from logarithm + -ic. Related: Logarithmical (1630s).
logged (adj.) Look up logged at Dictionary.com
"reduced to the condition of a log" (which was old sailors' slang for an incapacitated wooden ship), thus "inert in the water," c. 1820, from log (n.1).
logger (n.1) Look up logger at Dictionary.com
"one who fells or cuts trees," by 1708, agent noun from log (v.1).
logger (n.2) Look up logger at Dictionary.com
"one who enters data in a log," 1958, agent noun from log (v.2).
loggerhead (n.) Look up loggerhead at Dictionary.com
1580s, "stupid person, blockhead," perhaps from dialectal logger "heavy block of wood" + head (n.). Later it meant "a thick-headed iron tool" (1680s), a type of cannon shot, a type of turtle (1650s). Loggerheads "fighting, fisticuffs" is from 1670s, but the exact notion is uncertain, perhaps it suggests the heavy tools used as weapons. The phrase at loggerheads "in disagreement" is first recorded 1670s.
[W]e three loggerheads be: a sentence frequently written under two heads, and the reader by repeating it makes himself the third. [Grose, "Dictionary of the Vulgar Tongue," 1785]
loggia (n.) Look up loggia at Dictionary.com
"roofed galley used as an open-air room," 1742, from Italian loggia, from French loge (see lodge (n.)).
logging (n.1) Look up logging at Dictionary.com
"act of felling timber," 1706, verbal noun from log (v.1).
logging (n.2) Look up logging at Dictionary.com
"act of recording in a log," 1941, verbal noun from log (v.2).
loggy (adj.) Look up loggy at Dictionary.com
"heavy, sluggish," 1847, from log (n.1) + -y (2). Related: Logginess.
logic (n.) Look up logic at Dictionary.com
mid-14c., "branch of philosophy that treats of forms of thinking," from Old French logique (13c.), from Latin (ars) logica, from Greek logike (techne) "reasoning (art)," from fem. of logikos "pertaining to speaking or reasoning," from logos "reason, idea, word" (see logos). Meaning "logical argumentation" is from c. 1600.
logical (adj.) Look up logical at Dictionary.com
early 15c., "based on reason," from logic + -al (1). Meaning "pertaining to logic" is c. 1500. Attested from 1860 as "following as a reasonable consequence." Related: Logically.