The word whisky is not recorded before 1715, when it leapt into the lexicon with the sterling sentence "Whiskie shall put our brains in a rage." Philologists, though, are reasonably agreed that it comes from the Gaelic* uisge beatha meaning water of life.
Why? Because alcohol was already called aqua vitae in Latin. Alchemists, who were trying to turn base metal into gold, could find consolation for their failure in the fact that it's pretty damned easy to distil alcohol, which they called ardent spirits or aqua vitae.
The principle and the translation were not taken up solely by drunken Scotsmen. The Scandinavians called their home-brew aquavit, and the French called their brandy eau de vie.
However, the true water of life is a delightful euphemism for human urine. This should be drunk in moderation. Some say that it shouldn't be drunk at all, but urophagia is not to be sniffed at. Morarji Desai, who was Prime Minister of India, used to start every day by drinking the liquor brewed in his own internal distillery, which he always referred to as "The water of life". He said that Gandhi did the same. The Gandhi Institute denies this, although Mahatma's shrine was recently washed in cow-piss.
*Not to be confused with a gay lick.