To give evidence. To inform. His pall nosed and he was twisted for a crack; his confederate turned king’s evidence, and he was hanged for burglary.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Nose-1 * To Nose-1Nathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes