Tom o' Bedlams
A race of mendicants. The Bethlem Hospital was made to accommodate six lunatics, but in 1644 the number admitted was forty-four, and applications were so numerous that many inmates were dismissed halfcured. These “ticket-of-leave men” used to wander about as vagrants, chanting mad songs, and dressed in fantastic dresses, to excite pity. Under cover of these harmless “innocents,” a set of sturdy rogues appeared, called Abram men, who shammed lunacy, and committed great depredations.
“With a sigh like Tom o' Bedlam.”
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894