A one-horse chaise, said to be so called by a Lord Chief Justice, from their being so frequently used on Sunday jaunts by extravagant shop-keepers and tradesmen.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
bang straw * banks’s horseNathan Bailey's 1721 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes