Haymarket

The street was London's best known market for sex, and the slang treated the women as stock.

The Haymarket, running south from Piccadilly Circus past the Theatre Royal, was the most notorious pickup ground in early nineteenth century London, at its busiest once the theaters emptied. The phrase is built like trade tags such as Brummagem ware for the cheap and showy goods of Birmingham. It survives today mostly in Regency romance novels, from Georgette Heyer onward.