(2 syl.). It was Burke who first called the mob “the great unwashed,” but the term “unwashed” had been applied to them before, for Gay uses it.
The king of late drew forth his sword (Thank God, `twas not in wrath), And made, of many a squire and lord, An unwashed knight of Bath.
A Ballad on Quadrille.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Unwashed from Infoplease: