1680s, "disorderly part of the population, rabble, common mass, the multitude, especially when rude or disorderly; a riotous assemblage," slang shortening ofmobile,mobility "common people, populace, rabble" (1670s, probably with a conscious play onnobility), from Latinmobile vulgus "fickle common people" (the Latin phrase is attested c. 1600 in English), frommobile, neuter ofmobilis "fickle, movable, mobile" (seemobile (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.

word-forming element forming nouns meaning "rule or government by," from French-cratie or directly from Medieval Latin-cratia, from Greek-kratia "power, might; rule, sway; power over; a power, authority," fromkratos "strength" (from PIE*kre-tes- "power, strength," suffixed form of root*kar- "hard").

Productive in English from c. 1800, the connective-o- has come to be viewed as part of it.

Proto-Indo-European root meaning "to go, move, transport in a vehicle."

The rootwegh-, "to convey, especially by wheeled vehicle," is found in virtually every branch of Indo-European, including now Anatolian. The root, as well as other widely represented roots such asaks- andnobh-, attests to the presence of the wheel — and vehicles using it — at the time Proto-Indo-European was spoken. [Watkins, p. 96]

It might form all or part of:always;away;convection;convey;convex;convoy;deviate;devious;envoy;evection;earwig;foy;graywacke;impervious;invective;inveigh;invoice;Norway;obviate;obvious;ochlocracy;ogee;pervious;previous;provection;quadrivium;thalweg;trivia;trivial;trivium;vector;vehemence;vehement;vehicle;vex;via;viaduct;viatic;viaticum;vogue;voyage;wacke;wag;waggish;wagon;wain;wall-eyed;wave (n.);way;wee;weigh;weight;wey;wiggle.

It might also be the source of: Sanskritvahati "carries, conveys,"vahitram,vahanam "vessel, ship;" Avestanvazaiti "he leads, draws;" Greekokhos "carriage, chariot;" Latinvehere "to carry, convey,"vehiculum "carriage, chariot;" Old Church Slavonicvesti "to carry, convey,"vozŭ "carriage, chariot;" Russianpovozka "small sled;" Lithuanianvežu, vežti "to carry, convey,"važis "a small sled;" Old Irishfecht "campaign, journey,"fen "carriage, cart;" Welshgwain "carriage, cart;" Old Englishwegan "to carry;" Old Norsevegr, Old High Germanweg "way;" Middle Dutchwagen "wagon."