An overabundant commodity or service for which there is little or no demand. This expression clearly predates modern times, since drugs on the market, both illegal and legal, now are very profitable indeed. The English clergyman Thomas Fuller (The History of the Worthies of England, 1662) wrote, “He made such a vent for Welsh cottons, that what he found drugs at home, he left dainties beyond the sea.” The OED suggests that “drug” here has some different meaning but does not come up with a convincing explanation. Another writer suggests it may come from the French drogue, for “rubbish,” which makes more sense.