1875, from Italian Mafia "Sicilian secret society of criminals" (the prevailing sense outside Sicily), earlier, "spirit of hostility to the law and its ministers." A member is a mafioso (1870), fem. mafiosa, plural mafiosi, and this may be the older word in this sense. Arabic is often cited as the ultimate source (the Arabs ruled Sicily for more than two centuries in the Middle Ages), but which Arabic word is a matter of disagreement.
The most likely origin of the actual meaning of mafioso and its derivative mafia — as suggested by the nineteenth-century Sicilian ethnographer Giuseppe Pitrè — is a play by Placido Rizzoto, I Mafiusi della Vicaria, first performed in 1863. ... The play concerns a group of prisoners in the Palermo jail who command particular respect: although individualistic and quarrelsome, they are members of an association with distinct patterns of behavior (including an initiation ritual) and a hierarchy, which claims it can influence the political and administrative system of the island. [Diego Gambetta, "The Sicilian Mafia," Harvard, 1993]
The immediate source of mafioso, then, would be 19c. Sicilian mafiusu, "signifying a bully, arrogant but also fearless, enterprising, and proud" [Gambetta], who favors as the Arabic source an adjective from marfud "rejected."
1963, "the Mafia in America," Italian, literally "this thing of ours."
Mafia code of obedience to the leader and silence about the organization and its business, 1909, from Italian omertà, a dialectal form of umilta "humility," in reference to submission of individuals to the group interest, from Latin humilitas "lowness, small stature; insignificance; baseness, littleness of mind," in Church Latin "meekness," from humilis "lowly, humble," literally "on the ground," from humus "earth," from PIE root *dhghem- "earth."
1680s, "disorderly part of the population, rabble, common mass, the multitude, especially when rude or disorderly; a riotous assemblage," slang shortening of mobile, mobility "common people, populace, rabble" (1670s, probably with a conscious play on nobility), from Latin mobile vulgus "fickle common people" (the Latin phrase is attested c. 1600 in English), from mobile, neuter of mobilis "fickle, movable, mobile" (see mobile (adj.)).
Mob is a very strong word for a tumultuous or even riotous assembly, moved to or toward lawlessness by discontent or some similar exciting cause. Rabble is a contemptuous word for the very lowest classes, considered as confused or without sufficient strength or unity of feeling to make them especially dangerous. [Century Dictionary, 1897]
Also used of a promiscuous aggregation of people in any rank of life (1680s), and in Australia and New Zealand used without disparagement for "a crowd." Meaning "gang of criminals working together" is from 1839, originally of thieves or pick-pockets; the American English sense of "organized crime in general" is from 1927.
The Mob was not a synonym for the Mafia. It was an alliance of Jews, Italians, and a few Irishmen, some of them brilliant, who organized the supply, and often the production, of liquor during the thirteen years, ten months, and nineteen days of Prohibition. ... Their alliance — sometimes called the Combination but never the Mafia — was part of the urgent process of Americanizing crime. [Pete Hamill, "Why Sinatra Matters," 1998]
Mob scene "crowded place" is by 1922, from earlier use in reference to movies and theatrical productions; mob-rule "ochlocracy" is by 1806.
It forms all or part of: achieve; behead; biceps; cabbage; cabochon; caddie; cadet; cap; cap-a-pie; cape (n.1) "garment;" cape (n.2) "promontory;" capital (adj.); capital (n.3) "head of a column or pillar;" capitate; capitation; capitulate; capitulation; capitulum; capo (n.1) "leader of a Mafia family;" capo (n.2) "pitch-altering device for a stringed instrument;" caprice; capsize; captain; cattle; caudillo; chapter; chef; chief; chieftain; corporal (n.); decapitate; decapitation; forehead; head; hetman; kaput; kerchief; mischief; occipital; precipice; precipitate; precipitation; recapitulate; recapitulation; sinciput; triceps.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit kaput-; Latin caput "head;" Old English heafod, German Haupt, Gothic haubiþ "head."