Scotch Whiskey, often simply called Scotch, is malt Whiskey or grain Whiskey made in Scotland. Scotch Whiskey must be made in a manner specified by law. All Scotch Whiskey was originally made from malted barley. Commercial distilleries began introducing Whiskey made from wheat and rye in the late 18th century.[2] Scotch Whiskey is divided into five distinct categories: single malt Scotch Whiskey, single grain Scotch Whiskey, blended malt Scotch Whiskey (formerly called "vatted malt" or "pure malt"), blended grain Scotch Whiskey, and blended Scotch Whiskey. All Scotch Whiskey must be aged in oak barrels for at least three years. Any age statement on a bottle of Scotch Whiskey, expressed in numerical form, must reflect the age of the youngest Whiskey used to produce that product. A Whiskey with an age statement is known as guaranteed-age Whiskey. The first written mention of Scotch Whiskey is in the Exchequer Rolls of Scotland, 1495. A friar named John Cor was the distiller at Lindores Abbey in the Kingdom of Fife. Many Scotch Whiskey drinkers will refer to a unit for drinking as a dram.