A hanger on, or dependant; an allusion to the field burrs, which are not easily got rid of. Also the Northumbrian pronunciation: the people of that country, but chiefly about Newcastle and Morpeth, are said to have a burr in their throats, particularly called the Newcastle burr.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
See also the definition in Nathan Bailey's 1736 dictionary of canting and thieving slang.
Burnt * Bushel BubbyNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes