“Slang is the speech of him who robs the literary garbage carts on their way to the dumps.”

1880s, Plea for Free Speech in Boston (1880)

Prejudices, Fourth Series (1924)
1920s

( « L'argot est né de la haine, il n'existe plus» Arts, 6. February 1957. in À l’agité du bocal et autres textes, (op. cit.) p. 55.

Source: Dancing in the Flames (1997), p. 174

Cassinus and Peter: A Tragical Elegy (1734); reported in Bartlett's Familiar Quotations, 10th ed. (1919)

Source: Catch-22 (1961)
Context: Yossarian was cold, too, and shivering uncontrollably.... It was easy to read the message in his entrails. Man was matter, that was Snowden's secret. Drop him out a window and he'll fall. Set fire to him and he'll burn. Bury him and he'll rot, like other kinds of garbage. The spirit gone, man is garbage. That was Snowden's secret. Ripeness was all.

Attributed without citation in Young, David. Breakthrough Power for Golfers: A Daily Guide to an Extraordinary Life, Wind Runner Press, 2011. p. 189.

Attributed to Einstein by his colleague Léopold Infeld in his book Quest: An Autobiography (1949), p. 291 http://books.google.com/books?id=fsvXYpOSowkC&q=%22garbage+man%22#v=snippet&q=%22garbage%20man%22&f=false
Attributed in posthumous publications

" A Defense of Slang http://books.google.com/books?id=8WpaAAAAMAAJ&q="all+slang+is+metaphor+and+all+metaphor+is+poetry"&pg=PA110#v=onepage"
The Defendant (1901)