An importunate creditor. Dunny, in the provincial dialect of several counties, signifies deaf; to dun, then, perhaps may mean to deafen with importunate demands: some derive it from the word donnez, which signifies give. But the true original meaning of the word, owes its birth to one Joe Dun, a famous bailiff of the town of Lincoln, so extremely active, and so dexterous in his business, that it became a proverb, when a man refused to pay, Why do not you dun him? that is, Why do not you set Dun to arrest him? Hence it became a cant word, and is now as old as since the days of Henry VII. Dun was also the general name for the hangman, before that of Jack Ketch.
And presently a halter got,
Made of the best strong hempen teer,
And ere a cat could lick her ear,
Had tied it up with as much art,
As DUN himself could do for’s heart.
Cotton’s Virgil Trav. book iv.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Dumps * DunakerNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes