To talk thick and fast, as great praters usually do, to chatter like a magpye; also to speak a foreign language. He jabbered to rne in his damned outlandish parlez vous, but I could not understand him; he chattered to me in French, or some other foreign language, but I could not understand him.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
JackNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes