The Welsh version is wysgi. The name is derived from Gaelic uisge beatha (water of life). (Other countries also have their own "water of life": see the Scandinavian Akvavit or Italian Grappa, whose name derives from the Latin aqua vitae.)
Irish whiskey is typically distilled three times from a mash of several grains. Scottish whisky, properly called Scotch, is typically distilled twice, either from barley malt alone (see single malt whisky), or from barley malts and other grain malts which are then mixed together. Kentucky whiskey, called Bourbon, is normally only distilled once, as are most other American and Canadian whiskies.
Whisky is sold in several styles. Malt whisky consists of whisky made from 100 percent malted barley, whereas malt whisky from one distillery, rather than blended, is called single malt. The grains used to make malt whisky include Barley in Ireland, Scotland, Canada, and the United States, Rye in Canada and the United States. Pure pot still whiskey is made in Ireland from a combination of malted and unmalted barley. Various types of straight whiskey, such as Rye whiskey, Tennessee whiskey, and Bourbon whiskey which are produced in the U.S. are aged in new, charred, oak barrels. Blended whisky is made from a combination of any of the above whiskies with the similar Grain whisky or neutral grain spirits, which are much less expensive to produce than the other types of whisky. Blends will almost always identify the type of base whisky used, ie. blended Scotch, blended Canadian, or blended Bourbon. Light whiskey is a style of American whiskey made up almost entirely of neutral grain spirits, with small amounts (typically less than 5 - 10 percent total volume) of straight whiskey and Sherry added for flavor and coloring.
At one time much of the whiskey produced in the U.S. was "Bottled-in-Bond" according to the dictates of an 1898 Act of Congress; this practice has been largely discontinued, because one of the requirements of the Act was that such whiskey be produced at 100 U.S. Alcoholic proof (50% alcohol by volume). Whiskey this potent is rare in the U.S. anymore, partially because of changing public tastes but also because an alcoholic content so high is illegal in many countries, limiting the export market for it.