What a difference just one letter can make. Whiskey and whisky aren’t just two ways to spell the same thing. Whether or not the “e” is there can tell you a lot about the spirit. Primarily, where in the world the liquor originated. Basically, "whiskey" is from Ireland and America, while "whisky" is from pretty much everywhere else (Scotland, Canada, Japan, India, the rest of Europe, etc.).
Those who pledge allegiance to whiskey (or whisky) are incredibly protective of their particular spellings. After Eric Asimov of The New York Times published a column on Speyside single malts using the spelling with an “e” throughout, he received a spirited backlash from Scottish and Scotchophilic drinkers, which prompted the publication to update its venerated style guide. (The Supercall style guide has always noted the different spellings, using “whiskey” as the unspecified default.)
But the difference runs deeper than spellcheck, all the way back to the origin of whiskey itself. Here’s exactly what’s in a name.
The first recorded mention of whiskey comes from the Emerald Isle in 1405. The Irish Annals of Clonmacnoise refers to the drink by the Latin aqua vitae or “water of life.” Irish monks translated the term directly into Gaelic as ulisce beatha, which in turn was bastardized by English invaders into something like “uskey.” From there it was just a hop, skip and a mumble to “whiskey.”
Just across the Irish Sea, the Scots were drinking a very similar aqua vitae around the same time and made a very similar translation of the Latin into the Scottish Gaelic uisge-beatha. But the Scottish interpretation of the term resulted in the spelling “whisky.”
As long as we’re on the subject of scotch, it’s “scotch” for the spirit generally and “Scotch” only when you are using the word as a modifier for whisky.
America: Whiskey and Whisky
When Scottish and Irish immigrants arrived in the U.S. with their respective bottles of whisk(e)y, they sparked a mild marketing war. According to Mens Journal, some brands, like Maker’s Mark, opted for the Scottish spelling of the word to evoke the Scottish heritage of the distilling family, while others, like George Dickel, did so to take advantage of positive customer associations with quality Scotch whisky. The Standards of Identity for Distilled Spirits, American regulations regarding booze, also refers to “whisky” throughout.
But most distillers decided to follow the Irish spelling, either to market themselves to Irish drinkers or out of belief that the Irish variety actually connoted higher quality. According to the series "Distiller Magazine," after 1960, newspaper style guides like AP and the Los Angeles Times played a major role in cementing the spelling with an “e” for American whiskey (though interestingly, The New York Times was on the other side of the debate, spelling it the Scottish way until 1999 when it added the “e” in all cases, making absolutely nobody happy.)
Scottish immigrants were primarily responsible for starting up the whisky business in Canada. John Molson, credited with launching the first Canadian distillery in 1799, adopted Scottish distilling practices (augmented with a helping of rye, thenceforth signature to Canadian whisky) and employed Scottish distillers, and therefore used the Scottish spelling. After him, everyone just followed suit.
Shinjiro Torii, the founder of Suntory, constructed the first Japanese distillery in Yamazaki in 1923 based on Scottish distilling methods. Ever since, Japanese whisky has mirrored scotch, including in name.
In the early 19th century, Tasmanians followed scotch distilling practices imported by the British. Though Tasmania banned distilling in 1839, Australian craft distilling rose like a phoenix in 1997, instilling the same distilling and grammatical styles.
“Whisky” in India is mostly made with neutral grain spirits and molasses, making it more like rum than what we think of as whisky. The few brands that do make true whisky from malted barley, like Amrut Distilleries, do so in the Scottish style, inspired by the scotch introduced to India during the British Raj.
The Rest of Europe: Whisky
Other whisky-producing European nations like Finland and Germany generally follow Scotland.