This system was introduced in the 18th century. The British claim that this term has a nautical background. Every evening, sailors would line up for their daily quota of grog/rum. This had to first be proved to be as strong as promised and not watered down. The spirit was tested with gunpowder: a mixture of water and alcohol "proved" itself when it could be poured on a small amount of gunpowder and still light up the wet powder. If the powder did not ignite, the mixture had too much water in it and the grog was considered below proof. It might have happened earlier, as the Americans claim that this definition came about in the 17th century when European traders began making a large quantity of distilled spirits and wine available to American Indians. The very same process led to the nickname "firewater", this time given by Native Americans. There is no record of the finite strength of the distilled spirits in the context of its sale to or consumption by Native Americans.