Online Etymology Dictionary

marchioness (n.): 16c., from Medieval Latin marchionissa, fem. of marchio "marquis," from marca (see marquis (n.)).
Marcia: fem. proper name, from Latin Marcia, fem. of Marcius, a Roman gens, related to Marcus (q.v.).
Marcionite (n.): 1540, early Christian sect, named for Gnostic Marcion of Sinope (c.140), who denied any connection between the Old Testament and the New. They contrasted the barbaric and incompetent creator in the Old Testament, who favored bandits and killers, with the "higher god" of Christ. They also emphasized virginity and rejection of marriage. They flourished, especially in the East, until late 4c.
Marcomanni: name of a Teutonic tribe, from Latin Marcomanni, from a Germanic compound, literally "men of the border;" cf. Old High German mark, Old English mearc "border" (see march (n.2)). For second element, see man (n.).
Marcus: masc. proper name, from Latin Marcus, Roman praenomen, traditionally said to be related to Mars, Roman god of war.
Mardi Gras (n.): 1690s, from French, literally "fat Tuesday," from mardi "Tuesday" (12c., from Latin Martis diem "day of the planet Mars;" see Tuesday) + gras "fat," from Latin crassus, "thick." Day of eating and merrymaking before the fasting season of Lent.
mare (n.1): "female horse," Old English mere (Mercian), myre (West Saxon), fem. of mearh "horse," from Proto-Germanic *markhjon- (cf. Old Saxon meriha, Old Norse merr, Old Frisian merrie, Dutch merrie, Old High German meriha, German Mähre "mare"), said to be of Gaulish origin (cf. Irish and Gaelic marc, Welsh march, Breton marh "horse"). No known cognates beyond Germanic and Celtic. As the name of a throw in wrestling, it is attested from c.1600. Mare's nest "illusory discovery, excitement over something which does not exist" is from 1610s.
mare (n.2): "broad, dark areas of the moon," 1765, from Latin mare "sea" (see marine), applied to lunar features by Galileo and used thus in 17c. Latin works. They originally were thought to be actual seas.
mare (n.3): "night-goblin, incubus," Old English mare "incubus, nightmare, monster," from mera, mære, from Proto-Germanic *maron "goblin" (cf. Middle Low German mar, Middle Dutch mare, Old High German mara, German Mahr "incubus," Old Norse mara "nightmare, incubus"), from PIE *mora- "incubus" (cf. first element in Old Irish Morrigain "demoness of the corpses," literally "queen of the nightmare," also Bulgarian, Serbian mora, Czech mura, Polish zmora "incubus;" French cauchemar, with first element from Old French caucher "to trample"), from root *mer- "to rub away, harm" (see morbid).
Margaret: fem. proper name (c.1300), from Old French Margaret (French Marguerite), from Late Latin Margarita, female name, literally "pearl," from Greek margarites (lithos) "pearl," of unknown origin, "probably adopted from some Oriental language" [OED]; cf. Sanskrit manjari "cluster of flowers," also said by Indian linguists to mean "pearl," cognate with manju "beautiful." Arabic marjan probably is from Greek, via Syraic marganitha. The word was widely perverted in Germanic languages by folk-etymology, cf. Old English meregrot, which has been altered to mean literally "sea-pebble."
margaric (adj.): 1819, from French margarique (Chevreul), from Greek margaron "pearl" + -ic. Obsolete in science.
margarin (n.): 1836, from French margarine, a chemical term given to a fatty substance obtained from animal and vegetable oil, coined by French chemist Michel Eugène Chevreul (1786-1889) in 1813 from (acide) margarique "margaric (acid);" literally "pearly," from Greek margarites "pearl" (see Margaret). So called for the luster of the crystals. Now discarded in this sense as a chemical term, but preserved in margarine.
margarine (n.): butter substitute, 1873, from French margarine (see margarine). Invented 1869 by French scientist Hippolyte Mège-Mouries and made in part from edible fats and oils.
The "enterprising merchant" of Paris, who sells Margarine as a substitute for Butter, and does not sell his customers by selling it as Butter, and at Butter's value, has very likely found honesty to be the best policy. That policy might perhaps be adopted with advantage by an enterprising British Cheesemonger. ["Punch," Feb. 21, 1874]
Margarita (n.): cocktail made with tequila, 1963, from the fem. proper name, the Spanish form of Margaret. Earlier "a Spanish wine" (1920).
margarite (n.): "a pearl," late Old English, from Late Latin margarita (see Margaret). Figuratively, "that which is precious or excellent, a priceless quality or attribute;" also used as an epithet for Christ, Mary, etc., late 13c. Also margerie (mid-14c.).
marge (n.): "edge, border," 1560s, now chiefly poetic, shortening of margin (n.).
Margery: fem. proper name, from Old French Margerie, related to Late Latin margarita "pearl" (see Margaret).
margin (n.): mid-14c., "edge of a sea or lake;" late 14c., "space between a block of text and the edge of a page," from Latin marginem (nominative margo) "edge, brink, border, margin," from PIE *merg- "edge, border, boundary" (see mark (n.1)). General sense of "boundary space; rim or edge of anything" is from late 14c. Meaning "comfort allowance, cushion" is from 1851; margin of safety first recorded 1888. Stock market sense of "sum deposited with a broker to cover risk of loss" is from 1848. Related: Margins.
margin (v.): c.1600, "to furnish with marginal notes," from margin (n.). From 1715 as "to furnish with a margin."
marginal (adj.): 1570s, "written on the margin," from Medieval Latin marginalis, from Latin margo (see margin). Sense of "of little effect or importance" first recorded 1887. Related: Marginally.
marginalia (n.): 1832, from Latin marginalia, neuter plural of adjective marginalis "marginal," from marginis (see margin).
marginalise (v.): chiefly British English spelling of marginalize (q.v.); for suffix, see -ize. Related: marginalisation; marginalised; marginalising.
marginality (n.): 1849, from marginal + -ity.
marginalization (n.): 1974, from marginalize + -ation.
marginalize (v.): 1832, "to make marginal notes," from marginal + -ize. The meaning "force into a position of powerlessness" attested by 1929. Related: Marginalized; marginalizing.
margrave (n.): military governor of a German border province, 1550s, from Middle Dutch markgrave (Dutch markgraaf), literally "count of the border," from Old High German marcgravo; second element from graf "count, earl" (Old High German gravo, gravjo), from West Germanic *grafa "a designation of rank, possibly borrowed from Greek grapheus "scribe." For first element see mark (n.1). Later a hereditary title under the Holy Roman Empire. His wife was a margravine.
marguerite (n.): "oxeye daisy," 1866, from French marguerite (see Margaret). "According to French etymologists, this use of F. marguerite is not from the personal name, but comes directly from the sense 'pearl.' " [OED] In Middle English, margaret "a daisy" is attested from early 15c.
Maria: fem. proper name, from Late Latin; see Mary.
mariachi (n.): "Mexican strolling musical band," 1941, from Mexican Spanish, from French mariage "marriage" (see marriage), so called because such bands performed at wedding celebrations. As an adjective by 1967.
Marian (adj.): "of Mary," 1701, referring to the Virgin; also (c.1600) in reference to the reign of Mary Queen of England (1553-58); and (1902) to Mary Queen of Scots (1542-1587).
Marian: fem. proper name, collateral form of Marion, a diminutive of French Marie (see Mary), but often taken for a compound of Mary and Anne.
Marianne: fem. proper name, from French, a variant of Marian; sometimes anglicized as Mary Anne. Name of a republican secret society formed in France in 1851, hence "personification of the French Republic."
Marie Antoinette: queen consort of Louis XVI (1755-1793); as a decorative style, from 1925.
marigold (n.): late 14c., marygolde, from Mary (probably a reference to the Virgin) + gold, for color. The Old English name for the flower was simply golde.
marijuana (n.): 1918, altered by influence of Spanish proper name Maria Juana "Mary Jane" from mariguan (1894), from Mexican Spanish marihuana, of uncertain origin.
Marijuana ... makes you sensitive. Courtesy has a great deal to do with being sensitive. Unfortunately marijuana makes you the kind of sensitive where you insist on everyone listening to the drum solo in Iron Butterfly's 'In-a-Gadda-Da-Vida' fifty or sixty times. [P.J. O'Rourke, "Modern Manners," 1983]
Marilyn: fem. proper name, a diminutive of Mary.
marimba (n.): 1704, from an African language, probably Bantu (cf. Kimbundu and Swahili marimba, malimba, name of a xylophone-like instrument).
marina (n.): 1805, "a promenade by the sea," from Spanish or Italian marina "shore, coast," from Latin marinus (see marine (adj.)). Meaning "dock or basin with moorings for yachts and small craft" is 1935, American English.
marinade (n.): 1704, from French marinade "spiced vinegar or brine for pickling," from mariner "to pickle" (see marinate). As a verb from 1680s. Related: Marinaded; marinading.
marinate (v.): 1640s, from French mariner "to pickle in (sea) brine," from Old French marin (adj.) "of the sea," from Latin marinus (see marine (adj.)). Related: Marinated; marinating.
marine (adj.): early 15c., "pertaining to the sea," from Middle French marin, from Old French marin "of the sea, maritime," from Latin marinus "of the sea," from mare "sea, the sea, seawater," from PIE *mori- "body of water, lake" (see mere (n.)).
marine (n.): 14c., "seacoast;" see marine (adj.). Meaning "collective shipping of a country" is from 1660s. Meaning "soldier who serves on a ship" is from 1670s, a separate borrowing from French marine, from the French adjective. Phrase tell that to the marines (1806) originally was the first half of a retort expressing skepticism:
"Upon my soul, sir," answered the lieutenant, "when I thought she scorned my passion, I wept like a child."

"Belay there!" cried the captain; "you may tell that to the marines, but I'll be d----d if the sailors will believe it." ["John Moore," "The Post-Captain; or, the Wooden Walls Well Manned," 1805]
The book, a rollicking sea romance/adventure novel, was popular in its day and the remark is a recurring punch line in it (repeated at least four times). It was written by naval veteran John Davis (1774-1854) but published under the name John Moore. Walsh records that, "The marines are among the 'jolly' jack-tars a proverbially gullible lot, capable of swallowing any yarn, in size varying from a yawl-boat to a full-rigged frigate."
mariner (n.): mid-13c., from Anglo-French mariner, Old French marinier "seaman, sailor" (12c.), from Medieval Latin marinarius "sailor," from Latin marinus "of the sea" (see marine). Earlier and long more common than sailor. A sailor also could be a brimgeist in Old English.
Mariolatry (n.): "worship of the Virgin Mary," 1610s, from Mary + -latry, with connective element -o-.
Marion: fem. proper name, French, a diminutive of Marie (see Mary).
marionette (n.): puppet worked by strings, c.1620, literally "little little Mary," from French marionette (16c.), diminutive of Old French mariole "figurine, idol, picture of the Virgin Mary," diminutive of Marie (see Mary).
marish (n.): "a marsh," early 14c., mares, from Old French marois "marshland, bog" (12c., Modern French marais), from Frankish *marisk or some other Germanic source akin to marsh.
marital (adj.): c.1600, from French maritale and directly from Latin maritalis "of or belonging to married people," from maritus "married man, husband" (see marry).
maritime (adj.): 1540s, "of or pertaining to the sea," from Middle French maritime (16c.) or directly from Latin maritimus "of the sea, near the sea," from mare (genitive maris) "sea" (see mere (n.)) + Latin ending -timus, originally a superlative suffix (cf. intimus "inmost," ultimus "last"), here denoting "close association with." Maritimes "seacoast regions of a country" is from 1590s; specifically of the southeasternmost provinces of Canada by 1926.
Marius: masc. proper name, from Latin Marius, name of a Roman gens.