When this word turned up in the Guardian in early April 2007, in an item about the conviction of a man involved in cocaine smuggling, I was surprised to learn it had nothing to do with the old craft of making wooden casks.
The report said that it referred to an ancient smugglers’ trick in which a vessel would approach a British port, attracting the attention of customs officers. Before it docked, however, it would rendezvous secretly with a local boat apparently on a legitimate errand and transfer its illicit cargo.
The Oxford English Dictionary doesn’t know about the term in this sense, but the one it does record also refers to small boats going out to sea to meet others for questionable purposes. Coopering began to be used in print around 1880 for the practice by which small boats would sail out from port to sell spirits, tobacco and other goods to fishermen at sea. The boats were called copers or coopers from a Dutch or Flemish word meaning to buy or trade; it’s a relative of the English term coper, a horse dealer, and of the old verb cheap, to buy or sell, which survives in the London street name Cheapside.
Though spelled kooper, the word was pronounced as koper in Dutch and so by the fishermen who were the boats’ clients, but it usually appeared in British newspaper reports as cooper, perhaps through a spelling confusion with the craft term.
The OED has an illuminating note: “The practice began in a comparatively innocent barter trade carried on by Dutch boats visiting the fishing fleets, when the latter fished in close to the land, off Camperdown and the Texel; but it led to the fitting out of ‘floating grog-shops’ to attend each fleet. Public attention was called to the demoralizing nature of the traffic in 1881, and it formed the subject of a convention between the British, German and Dutch governments in 1882, for the carrying out of which an Act of Parliament was passed in 1888.”