He beats Banaghan; an Irish saying of one who tells wonderful stories. Perhaps Banaghan was a minstrel famous for dealing in the marvellous.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
To Bamboozle * BandboxNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes