When I started drinking liquor I was told by the supposed old hands of the whiskey world that the only difference between whisky and whiskey was the letter "E", but the truth runs much deeper.
The spelling actually reveals where the liquor was made- if it's spelled with an "E" then it was made in Ireland or the U.S., if it's spelled without an "E" then it was made in Canada, Japan or Scotland.
So if country of origin is important to you then check the spelling, but if you're just trying to bend your elbow with a bit of brown then forget about the spelling and drink up, because it's all good!
-Via Tasting Table