Online Etymology Dictionary

monument (n.): late 13c., "a sepulchre," from Old French monument "grave, tomb, monument," and directly from Latin monumentum "a monument, memorial structure, statue; votive offering; tomb; memorial record," literally "something that reminds," from monere "to remind, warn" (see monitor (n.)). Sense of "structure or edifice to commemorate a notable person, action, or event" first attested c.1600.
monumental (adj.): c.1600, "pertaining to a monument," from Late Latin monumentalis "pertaining to a monument," from monumentum (see monument). From 1650s in the loose sense of "vast, stupendous." Related: Monumentally.
monumentalize (v.): 1857, from monmental + -ize. Related: Monumentalized; monumentalizing.
moo (v.): "to make the characteristic sound of a cow," 1540s, of imitative origin. Related: Mooed; mooing. The noun is from 1789. Baby-talk moo-cow (n.) attested from 1812.
mooch (v.): mid-15c., "pretend poverty," probably from Old French muchier, mucier "to hide, sulk, conceal, hide away, keep out of sight," of uncertain origin, perhaps from Celtic or Germanic (Liberman prefers the latter, Klein the former). Or the word may be a variant of Middle English mucchen "to hoard, be stingy" (c.1300), probably originally "to keep coins in one's nightcap," from mucche "nightcap," from Middle Dutch muste "cap, nightcap," ultimately from Medieval Latin almucia, of unknown origin. Sense of "sponge off others" first recorded 1857.
Whatever the distant origin of mooch, the verb *mycan and its cognates have been part of European slang for at least two millennia. [Liberman]
Related: Mooched; mooching. As a noun meaning "a moocher," from 1914.
moocher (n.): "beggar, scrounger," 1857, agent noun from mooch (v.).
mood (n.1): "emotional condition, frame of mind," Old English mod "heart, frame of mind, spirit; courage, arrogance, pride; power, violence," from Proto-Germanic *motha- (cf. Old Saxon mod "mind, courage," Old Frisian mod "intellect, mind, intention," Old Norse moðr "wrath, anger," Middle Dutch moet, Dutch moed, Old High German muot, German Mut "courage," Gothic moþs "courage, anger"), of unknown origin.

A much more vigorous word in Anglo-Saxon than currently, and used widely in compounds (e.g. modcræftig "intelligent," modful "proud"). To be in the mood "willing (to do something)" is from 1580s. First record of mood swings is from 1942.
mood (n.2): "grammatical form indicating the function of a verb," 1560s, an alteration of mode (n.1), but the grammatical and musical (1590s) usages of it influenced the meaning of mood (n.1) in phrases such as light-hearted mood.
moodiness (n.): Old English modignes "pride, passion, anger;" see moody + -ness. Meaning "condition of being moody" is from 1858.
moody (adj.): Old English modig "brave, proud, high-spirited, impetuous, arrogant," from Proto-Germanic *modago- (cf. Old Saxon modag, Dutch moedig, German mutig, Old Norse moðugr); see mood (1) + -y (2). Meaning "subject to gloomy spells" is first recorded 1590s (via a Middle English sense of "angry").
Moog (n.): 1969, from R.A. Moog, U.S. engineer who invented it.
moolah (n.): also moola, "money," c.1920, American English slang, of unknown origin.
moon (n.): Old English mona, from Proto-Germanic *menon- (cf. Old Saxon and Old High German mano, Old Frisian mona, Old Norse mani, Danish maane, Dutch maan, German Mond, Gothic mena "moon"), from PIE *me(n)ses- "moon, month" (cf. Sanskrit masah "moon, month;" Avestan ma, Persian mah, Armenian mis "month;" Greek mene "moon," men "month;" Latin mensis "month;" Old Church Slavonic meseci, Lithuanian menesis "moon, month;" Old Irish mi, Welsh mis, Breton miz "month"), probably from root *me- "to measure," in reference to the moon's phases as the measure of time.

A masculine noun in Old English. In Greek, Italic, Celtic, Armenian the cognate words now mean only "month." Greek selene (Lesbian selanna) is from selas "light, brightness (of heavenly bodies)." Old Norse also had tungl "moon," ("replacing mani in prose" - Buck), evidently an older Germanic word for "heavenly body," cognate with Gothic tuggl, Old English tungol "heavenly body, constellation," of unknown origin or connection. Hence Old Norse tunglfylling "lunation," tunglœrr "lunatic" (adj.).

Extended 1665 to satellites of other planets. To shoot the moon "leave without paying rent" is British slang from c.1823; card-playing sense perhaps influenced by gambler's shoot the works (1922) "go for broke" in shooting dice. The moon race and the U.S. space program of the 1960s inspired a number of coinages, including, from those skeptical of the benefits to be gained, moondoggle (cf. boondoggle). The man in the moon is mentioned since early 14c.; he carries a bundle of thorn-twigs and is accompanied by a dog. Some Japanese, however, see a rice-cake-making rabbit in the moon.
moon (v.): c.1600, "to expose to moonlight;" later "idle about" (1836), "move listlessly" (1848), probably on notion of being moonstruck. The meaning "to flash the buttocks" is first recorded 1968, U.S. student slang, from moon (n.) "buttocks" (1756), "probably from the idea of pale circularity" [Ayto]. See moon (n.). Related: Mooned; mooning.
moon-calf (n.): also mooncalf, "abortive, shapeless, fleshy mass," 1560s, attributed to the influence of the moon; from moon (n.) + calf (n.). In later 16c., "deformed creature, monster."
moon-dog (n.): one who bays at the moon, 1660s, from moon (n.) + dog (n.). Earlier in same sense was mooner (1570s).
moon-shot (n.): 1958, from moon (n.) + shot (n.).
moon-up (n.): "moonrise," U.S. dialectal, 1907, from moon (n.) + rise (n.).
moonbeam (n.): 1580s, from moon (n.) + beam (n.).
moonglow (n.): 1926, from moon (n.) + glow (n.).
Moonie (n.): 1974, a member of the Unification Church, headed by Sun Myung Moon.
moonless (adj.): c.1500, from moon (n.) + -less.
moonlight (v.): "hold a second job, especially at night," 1957 (implied in moonlighting), from moonlighter (1954), from the notion of working by the light of the moon; see moonlight (n.). Related: Moonlighting. Earlier the word had been used to mean "commit crimes at night" (1882).
moonlight (n.): "light of the moon," mid-14c., from moon (n.) + light (n.).
moonlit (adj.): 1830 (first attested in Tennyson), from moon (n.) + lit.
moonrace (n.): also moon race, "national rivalry to be first to send humans to the moon," 1963, from moon (n.) + race (n.1).
moonraker (n.): in England, a name traditionally given to Wiltshire people, attested from 1787, is from the stock joke about fools who mistook the reflection of the moon in a pond for a cheese and tried to rake it out. But as told in Wiltshire, the men were surprised trying to rake up kegs of smuggled brandy, and put off the revenuers by acting foolish.
moonrise (n.): 1728, from moon (n.) + rise (n.).
moonscape (n.): 1926, from moon (n.) + scape (n.).
moonshine (n.): c.1500, "moonlight," from moon (n.) + shine (n.). In figurative use, implying "appearance without substance," from late 15c.; perhaps connected in that sense with notion of "moonshine in water" (cf. moonraker). Meaning "illicit liquor" is attested from 1785 (earliest reference is to that smuggled on the coasts of Kent and Sussex); moonlight also occasionally was used in this sense early 19c. As a verb from 1883. Related: Moonshiner (1860).
moonstruck (adj.): 1670s, from moon (n.) + struck (see strike (v.)). Cf. Greek selenobletos. For sense, cf. moon (v.). Perhaps coined by Milton.
moonwalk (n.): "a walking on the moon," 1966, from moon (n.) + walk (n.).
moony (adj.): 1580s, "like the moon;" 1848, "dreamy, listless," from moon (n.) + -y (2). Cf. moon (v.).
moor (v.): "to fasten (a vessel) by a cable," late 15c., probably related to Old English mærels "mooring rope," via unrecorded *mærian "to moor," or possibly borrowed from Middle Low German moren or Middle Dutch maren "to moor," from West Germanic *mairojan. Related: Moored, mooring. French amarrer is from Dutch.
moor (n.): "waste ground," Old English mor "morass, swamp," from Proto-Germanic *mora- (cf. Old Saxon, Middle Dutch, Dutch meer "swamp," Old High German muor "swamp," also "sea," German Moor "moor," Old Norse mörr "moorland," marr "sea"), perhaps related to mere (n.), or from root *mer- "to die," hence "dead land."
The basic sense in place names is 'marsh', a kind of low-lying wetland possibly regarded as less fertile than mersc 'marsh.' The development of the senses 'dry heathland, barren upland' is not fully accounted for but may be due to the idea of infertility. [Cambridge Dictionary of English Place-Names]
Moor (n.): "North African, Berber," late 14c., from Old French More, from Medieval Latin Morus, from Latin Maurus "inhabitant of Mauritania" (northwest Africa, a region now corresponding to northern Algeria and Morocco), from Greek Mauros, perhaps a native name, or else cognate with mauros "black" (but this adjective only appears in late Greek and may as well be from the people's name as the reverse). Being a dark people in relation to Europeans, their name in the Middle Ages was a synonym for "Negro;" later (16c.-17c.) used indiscriminately of Muslims (Persians, Arabs, etc.) but especially those in India.
mooreeffoc (n.): "coffee-room, viewed from the inside through a glass door, as it was seen by Dickens on a dark London day; ... used by Chesterton to denote the queerness of things that have become trite, when they are seen suddenly from a new angle." [J.R.R. Tolkien]
mooring (n.): "place where a vessel can be moored," early 15c., "process of making a ship secure," verbal noun from moor (v.).
moorings (n.): 1744, "ropes, etc., by which a floating thing is made fast," from mooring. Figurative sense is from 1851.
Moorish (adj.): "of or pertaining to Moors," mid-15c., from Moor + -ish.
moorland (n.): Old English morlond; see moor (n.) + land (n.).
moose (n.): 1610s, from an Algonquian language, probably Narragansett moos or Abenaki moz (cf. Penobscot muns, Ojibwa mooz, Unami Delaware /mo:s/), said by early sources to be from moosu "he strips off," in reference to the animals' stripping bark for food.
moot (n.): "assembly of freemen," mid-12c., from Old English gemot "meeting" (especially of freemen, to discuss community affairs or mete justice), "society, assembly, council," from Proto-Germanic *ga-motan (cf. Old Low Frankish muot "encounter," Middle Dutch moet, Middle High German muoz), from collective prefix *ga- + *motan (see meet (v.)).
moot (adj.): "debatable; not worth considering" from moot case, earlier simply moot (n.) "discussion of a hypothetical law case" (1530s), in law student jargon. The reference is to students gathering to test their skills in mock cases.
moot (v.): "to debate," Old English motian "to meet, talk, discuss," from mot (see moot (n.)). Related: Mooted; mooting.
mop (n.): late 15c., mappe "bundle of yarn, etc., fastened to the end of a stick for cleaning or spreading pitch on a ship's decks," from Walloon (French) mappe "napkin," from Latin mappa "napkin" (see map (n.)). Modern spelling by 1660s. Of hair, from 1847.
mop (v.): 1709, from mop (n.). Related: Mopped; mopping.
mope (v.): 1560s, "to move and act unconsciously;" 1580s, "to be listless and apathetic," the sound of the word perhaps somehow suggestive of low feelings (cf. Low German mopen "to sulk," Dutch moppen "to grumble, to grouse," Danish maabe, dialectal Swedish mopa "to mope"). Related: Moped; moping; mopey; mopish.
moped (n.): 1956, from Swedish (c.1952), from (trampcykel med) mo(tor och) ped(aler) "pedal cycle with engine and pedals" (the earliest versions had auxiliary pedals). Cf. obsolete English mo-bike (1925), from motor bicycle.
moppet (n.): endearing term for a baby, a girl, etc., c.1600, from Middle English moppe "little child, baby doll" (mid-15c.) + -et, diminutive suffix. The Middle English word also meant "simpleton, fool," and may have been cognate with Low German mop "simpleton" [Barnhart]. Or, if "baby doll" is the original sense in Middle English, perhaps from Latin mappa "napkin, tablecloth," hence "rag doll."