Green’s Dictionary of Slang

a one-horse chaise.

c.1786		Grose Classical Dict. of the Vulgar Tongue ms. additions n.p.: Bankrupt Cart a One horse Chaise, so called as it is said by My Lord Mansfield, from their being so frequently used in Sundays jaunts, by extravagant Shopkeepers & other Tradesmen.
1788, 1796		Grose Classical Dict. of the Vulgar Tongue (2nd, 3rd edn) n.p.: Bankrupt Cart. 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.
1795		Temple of Folly! 7: O shame to reason, that such cobling Art / Should boast a carriage, alias Bankrupt Cart.
1811		Lex. Balatronicum.
1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc.