Online Etymology Dictionary

moleskin (n.): 1660s, from mole (2) + skin (n.).
molest (v.): late 14c., "to cause trouble, grief, or vexation," from Old French molester "to torment, trouble, bother" (12c.) and directly from Latin molestare "to disturb, trouble, annoy," from molestus "troublesome, annoying, unmanageable," perhaps related to moles "mass" (see mole (n.3)) on notion of either "burden" or "barrier." Meaning "sexually assault" first attested 1950. Related: Molested; molesting.
molestation (n.): c. 1400, "action of annoying or vexing," from Old French molestacion "vexation, harassing," and directly from Medieval Latin molestationem (nominative molestatio), noun of action from past participle stem of molestare (see molest). It meant "the harassing of a person in his possession or occupation of lands" in Scottish law; in English common law it came to mean "injury inflicted upon another."
molester (n.): 1570s, agent noun from molest.
Moll: female proper name, shortened form of Molly, itself familiar for Mary. Used from c. 1600 for "prostitute;" meaning "companion of a thief" is first recorded 1823. A general word for "woman" in old underworld slang, for instance Moll-buzzer "pickpocket who specializes in women;" Moll-tooler "female pick-pocket." U.S. sense of "a gangster's girlfriend" is from 1923.
mollification (n.): late 14c., from Old French mollificacion (Modern French mollification), from Medieval Latin mollificationem (nominative mollificatio), noun of action from past participle stem of mollificare (see mollify).
mollified (adj.): 1620s, past participle adjective from mollify.
mollify (v.): late 14c., "to soften (a substance)," from Old French mollifier or directly from Late Latin mollificare "make soft, mollify" from mollificus "softening," from Latin mollis "soft" (see melt (v.)) + root of facere "to make" (see factitious). Transferred sense of "soften in temper, appease, pacify" is recorded from early 15c. Related: Mollified; mollifying.
mollusc (n.): see mollusk.
Mollusca (n.): 1797, from Modern Latin mollusca, chosen by Linnaeus as the name of an invertebrate order (1758), from neuter plural of Latin molluscus "thin-shelled," from mollis "soft" (see melt (v.)). Linnæus applied the word to a heterogeneous group of invertebrates, not originally including mollusks with shells; the modern scientific use is after a classification proposed 1790s by French naturalist Georges Léopole Chrétien Frédéric Dagobert, Baron Cuvier (1769-1832).
mollusk (n.): 1783, mollusque (modern spelling from 1839), from French mollusque, from Modern Latin Mollusca (see Mollusca), the phylum name. Related: Molluscuous; molluscan.
molly (n.): seabird, 1857, short for mollymawk, from Dutch mallemok, from mal "foolish" + mok "gull."
Molly: fem. proper name, a familiar form of Mary.
Molly Maguire (n.): secret society in the mining districts of Pennsylvania, 1867 (suppressed 1876); named for earlier secret society formed in Ireland (1843) to resist payment of rents. From Molly (see Moll) + common Irish surname Maguire. Memebers were said to sometimes wear women's clothing as disguise.
mollycoddle (v.): also molly-coddle, 1870, from a noun (1833) meaning "one who coddles himself," from Molly (pet name formation from Mary), which had been used contemptuously since 1754 for "a milksop, an effeminate man," + coddle (q.v.). Related: Mollycoddled; mollycoddling.
Moloch: Canaanite god said to have been propitiated by sacrificing children (Lev. xviii:21), from Latin Moloch, from Greek Molokh, from Hebrew molekh, from melekh "king," altered by the Jews with the vowel points from basheth "shame" to express their horror of the worship.
Molotov cocktail (n.): 1940, a term from Russo-Finnish War (used and satirically named by the Finns), from Molotov (from Russian molot "hammer") name taken by Vyacheslav Mikhailovich Skriabin (1890-1986), Soviet minister of foreign affairs 1939-1949.
molt (v.): also moult, mid-14c., mouten, of feathers, "to be shed," from Old English *mutian "to change" (in bemutian "to exchange"), from Latin mutare "to change" (see mutable). Transitive sense, of birds, "to shed feathers" is first attested 1520s. With parasitic -l-, late 16c., on model of fault, etc. Related: Molted, moulted; molting, moulting. As a noun from 1815.
molten (adj.): late 13c., from archaic past participle of Old English meltian, a class III strong verb (see melt (v.)).
moly (n.): 1570s, fabulous magical herb with white flowers and black root, given by Hermes to Odysseus as protection against Circe's sorcery, of unknown origin.
molybdenum (n.): metallic element, 1816, from molybdena, used generally for lead-like minerals, from Greek molybdos "lead," also "black graphite," related to Latin plumbum "lead" (see plumb (n.)), and like it probably borrowed from a lost Mediterranean language, perhaps Iberian. The element so called because of its resemblance to lead ore.
mom (n.): 1867, American English, perhaps a shortening of mommy; also see mamma. Adjectival phrase mom and pop dates from 1951.
moment (n.): mid-14c., "very brief portion of time, instant," in moment of time, from Old French moment (12c.) "moment, minute; importance, weight, value" or directly from Latin momentum "movement, motion; moving power; alteration, change;" also "short time, instant" (also source of Spanish, Italian momento), contraction of *movimentum, from movere "to move" (see move (v.)). Some (but not OED) explain the sense evolution of the Latin word by notion of a particle so small it would just "move" the pointer of a scale, which led to the transferred sense of "minute time division." Sense of "importance, 'weight' " is attested in English from 1520s.

Phrase never a dull moment first recorded 1889 in Jerome K. Jerome's "Three Men in a Boat." Phrase moment of truth first recorded 1932 in Hemingway's "Death in the Afternoon," from Spanish el momento de la verdad, the final sword-thrust in a bull-fight.
momentarily (adv.): 1650s, "for a moment," from momentary + -ly (2). Meaning "at any moment" is from 1928.
momentary (adj.): "lasting a moment," mid-15c., from Latin momentarius "of brief duration," from momentum (see moment).
momently (adv.): 1670s, "moment to moment," from moment + -ly (2). Meaning "at any moment" is from 1775.
momento (n.): a misspelling, or perhaps variant, of memento.
momentous (adj.): 1650s, from moment + -ous to carry the sense of "important" while momentary kept the meaning "of an instant of time." Related: Momentously; momentousness.
momentum (n.): 1690s, scientific use in mechanics, "quantity of motion of a moving body," from Latin momentum "movement, moving power" (see moment). Figurative use dates from 1782.
momma (n.): 1884, American English variant of mamma (q.v.). As a biker's girlfriend or female passenger, from 1950s.
mommy (n.): 1844, U.S. variant of mamma. Variant spelling mommie attested by 1882. Mommy track first attested 1987. Related: Mommies; also see momma.
Momus (n.): "humorously disagreeable person," 1560s, from Latin, from Greek Momos, nme of the god of ridicule and sarcasm (Greek momos, literally "blame, ridicule, disgrace," of unknown origin); also used in English as personification of fault-finding and captious criticism.
momzer (n.): "contemptible person, moocher," 1560s, from Hebrew, literally "bastard" (used in Vulgate), but modern usage is a recent borrowing from Yiddish.
Mona: fem. proper name, from Irish Muadhnait, diminutive of muadh "noble."
Mona Lisa: by 1827 as the name of Leonardo's painting or its subject, Lisa, wife of Francesco del Giocondo (see Gioconda). Mona is said to be a contraction of madonna as a polite form of address to a woman, so, "Madam Lisa." The name is by 1923 (D.H. Lawrence) in reference to her enigmatic smile or expression.
monad (n.): "unity, arithmetical unit," 1610s, from Late Latin monas (genitive monadis), from Greek monas "unit," from monos "alone" (see mono-). In Leibnitz's philosophy, "an ultimate unit of being" (1748). Related: Monadic.
monarch (n.): mid-15c., from Middle French monarque (14c.) or directly from Late Latin monarcha, from Greek monarkhes "one who rules alone" (see monarchy). As a type of large butterfly, from 1890.
monarchic (adj.): from Middle French monarchique, from Greek monarkhikos, from monarkhes (see monarch). Related: Monarchical (1570s).
monarchism (n.): from French monarchisme, from monarchie (see monarchy).
monarchist (n.): 1640s, from monarchy + -ist. Related: Monarchistic.
monarchy (n.): "state ruled by monarchical government," mid-14c.; "rule by one person," late 14c.; from Old French monarchie "sovereignty, absolute power" (13c.), from Late Latin monarchia, from Greek monarkhia "absolute rule," literally "ruling of one," from monos "alone" (see mono-) + arkhein "to rule" (see archon).
monastery (n.): c. 1400, from Old French monastere "monastery" (14c.) and directly from Late Latin monasterium, from Ecclesiastical Greek monasterion "a monastery," from monazein "to live alone," from monos "alone" (see mono-). With suffix -terion "place for (doing something)." Originally applied to houses of any religious order, male or female.
monastic (adj.): mid-15c., from Middle French monastique "monkish, monastic," or directly from Late Latin monasticus, from Ecclesiastical Greek monastikos "solitary, pertaining to a monk," from Greek monazein "to live alone" (see monastery). Related: Monastical (c. 1400).
monasticism (n.): 1795, from monastic + -ism.
Monday (n.): second day of the week, Old English mondæg, monandæg "Monday," literally "day of the moon," from mona (genitive monan; see moon (n.)) + dæg (see day). Common Germanic (Old Norse manandagr, Old Frisian monendei, Dutch maandag, German Montag) loan-translation of Late Latin Lunæ dies, source of the day name in Romance languages (French lundi, Italian lunedi, Spanish lunes), itself a loan-translation of Greek selenes hemera. The name for this day in Slavic tongues generally means "day after Sunday."

Phrase Monday morning quarterback is attested from 1932, Monday being the first day back at work after the weekend, when school and college football games were played. Black Monday (mid-14c.) is the Monday after Easter day, though how it got its reputation for bad luck is a mystery. Saint Monday (1753) was "used with reference to the practice among workmen of being idle Monday, as a consequence of drunkenness on the Sunday" before [OED]. Clergymen, meanwhile, when indisposed complained of feeling Mondayish (1804) in reference to effects of Sunday's labors.
mondo (adj.): "very much, extreme," 1979, from Italian mondo "world," from "Mondo cane," 1961 film, literally "world for a dog" (English title "A Dog's Life"), depicting eccentric human behavior; the word was abstracted from the original title and taken as an intensifier.
monetarist (adj.): 1914, from monetary + -ist. Related Monetarism (1963).
monetary (adj.): "pertaining to money," 1802, from Late Latin monetarius "pertaining to money," originally "of a mint," from Latin moneta "mint, coinage" (see money). Related: Monetarily.
monetise (v.): chiefly British English spelling of monetize; for suffix, see -ize. Related: Monetise; monetising.
monetization (n.): 1864; see monetize + -ation.