According to Wikipedia, "whisky or whiskey is a type of distilled alcoholic beverage made from fermented grain mash." The word stems from the Gaelic word (uisceluisge) which means "water". It is a favorite among many, standing up on its own or in many mixed drink recipes. And no wonder, with so many types of whiskys - malt, Bourbon, Tennessee, and Scotch, just to name a few.
So why the two spellings?
It seems that the spelling difference is due to a regional variation (like color vs. colour).
"Whiskey" is more commonly preferred in Ireland, "whisky" is preferred by Canada, and the United States is a bit more inconsistent. That would make the plural formats read whiskeys and whiskies, respectively. According to the New York Times, many U.S. Scotch aficionados wrote to the newspaper about their preference of the spelling, "whisky".
Based on our research here, there is no real discernible difference between the spellings - apart from the different types of whisk(e)y, that is. At the end of the day, we still prefer to sip it... slowly.