The history of whisky/whiskey in Scotland and Ireland is slightly more complex than described in Thompson's post.

The art of distillation spread to Ireland and Scotland no later than the 15th century, as did the common European practice of distilling 'Aqua Vitae' or spirit alcohol primarily for medicinal purposes. The practice of medicinal distillation eventually passed from a monastic setting to the secular via professional medical practitioners of the time, The Guild of Surgeon Barbers. The first confirmed written record of whisky in Ireland comes from 1405, in the Irish Annals of Clonmacnoise, which attributes the death of a chieftain to "taking a surfeit of aqua vitae" at Christmas. In Scotland, the first evidence of whisky production comes from an entry in the Exchequer Rolls for 1494 where malt is sent "To Friar John Cor, by order of the king, to make aquavitae", enough to make about 500 bottles... After the English Malt Tax of 1725, most of Scotland's distillation was either shut down or forced underground. Scotch whisky was hidden under altars, in coffins, and in any available space to avoid the governmental excisemen or revenuers. Scottish distillers, operating out of homemade stills, took to distilling whisky at night when the darkness hid the smoke from the stills. For this reason, the drink became known as moonshine. At one point, it was estimated that over half of Scotland's whisky output was illegal. [Wikipedia]

But of course, the process is much older than that, going back into the 13th century...