"The (great) unwashed” means the masses, the multitudes, the hoi polloi, the common people, and other similar terms. In 1800, a Glasgow professor referred to mechanics as “unwashed artificers,” a term that became frequently used for the often-dirty skilled workers.
Edward Bulwer-Lytton’s novel, Paul Clifford (1830) coined “the great unwashed”:
“He is certainly a man who bathes and ‘lives cleanly’, (two especial charges preferred against him by Messrs. the Great Unwashed).”
Some political protests (such as Occupy Wall Street’s nicknames of “flea party” and “Poopstock”) have been described as being composed of “the great unwashed.”
Wikipedia: Hoi polloi
Hoi polloi (Ancient Greek: οἱ πολλοί), an expression meaning “the many”, or in the strictest sense, “the majority” in Greek, is used in English to denote “the masses” or “the people”, usually in a derogatory sense. Synonyms for “hoi polloi” include “... commoners, great unwashed, minions, multitude, plebeians, rank and file, Riff Raff, the common people, the herd, the many, the plebs, the proles, the peons, the working class”.
(Oxford English Dictionary)
unˈwashed, adj. and n.
spec. Of persons: not having washed; not usually washed or in a clean state.
a1616 Shakespeare King John (1623) iv. ii. 202 Another leane, vnwash’d Artificer, Cuts off his tale, and talkes of Arthurs death.
a1727 Ballad on Quadrille viii, The King of late‥made, of many a Squire and Lord, An unwash’d Knight of Bath.
People who are not usually in a clean state, regarded collectively; the ‘lower classes’. Freq. in “the great unwashed.”
1830 E. Bulwer-Lytton Paul Clifford I. p. xix, He is certainly a man who bathes and ‘lives cleanly’, (two especial charges preferred against him by Messrs. the Great Unwashed).
1833 T. Hook Parson’s Daughter II. vi. 119 The ‘fat and greasy’, and the ‘great unwashed’, bowed and smiled their best.
1840 Tipperary Constitution 21 Aug. 2/3 The learned gentleman then briefly addressed the few unwashed, who were attracted to the scene.
1849 Thackeray Pendennis (1850) I. xxx. 290 Gentlemen, there can be but little doubt that your ancestors were the Great Unwashed.
10 November 1819, Providence (RI) Patriot, pg. 2:
BOSTON, Nov. 8.
LATEST FROM ENGLAND.
If a decent tradesman came up to vote for Alderman Brydges, the Orator pointed him out for three groans; if “a lean unwashed artificer” tendered his suffrage for Wood and Thorp, the orator recommended him to his worthy friends “the Groundlings” for three cheers;...
October 1825, The Quarterly Review, pg. 411:
In the year 1800, Dr. Birkbeck, at that time professor in the Anderson College at Glasgow, announced a course of lectures on natural philosophy and its application to the arts, for the instruction of mechanics.
“I had frequent opportunities,” he says, “of observing the intelligent curiosity of the ‘unwashed artificers,’ to whose mechanical skill I was often obliged to have recourse;...—Mechanics’ Magazine, vol. i.
3 April 1829, The Lion (London), pg. 424:
For instance, the “ Times” has now running after it, all the unwashed followers of reform, of the late queen, and of Catholic emancipation.
By Edward Bulwer-Lytton
London: Henry Colburn and Richard Bentley
For though he is certainly a man who bathes and ‘lives cleanly’, (two especial charges preferred against him by Messrs. the Great Unwashed) ...
18 April 1840, The Chartist Circular (Glasgow), pg. 121:
With them all went on “merry as a marriage bell;” while the unwashed millions were vulgar enough to complain about oppression, and prophesy its consequences.
The Progressive Dictionary of the English Language,
A supplementary wordbook to all leading dictionaries of the United States and Great Britain
By Samuel Fallows
Chicago, IL: Progressive Pub. Co.
The unwashed, the great unwashed, the lower class of people. The latter phrase was first applied by Burke to the artisan class, but is now used to designate the lower class generally; the mob; the rabble.
OCLC WorldCat record
The great unwashed : a vindication of the rights of labour, and a plea for socialism
Author: T Stirling Ewing
Publisher: Manchester : John Heywood, 
Edition/Format: Book : English
OCLC WorldCat record
Washing “the great unwashed” : public baths in urban America, 1840-1920
Author: Marilyn T Williams
Publisher: Columbus : Ohio State University Press, ©1991.
Series: Urban life and urban landscape series.
Edition/Format: Book : State or province government publication : eBook : English
The Washington (DC) Times—Communities
Wall Street invaded by great unwashed leftist thugs
Sunday, October 2, 2011 - The Tygrrrr Express by Eric Golub
LOS ANGELES, October 3, 2011—All the money and power of Wall Street is not enough to prevent the angry, violent, leftist mobs from invading.
New York City • Government/Law/Politics/Military • (0) Comments • Friday, October 14, 2011 • Permalink