Under the Irish influence
"Whisky" is an English corruption of the ancient name for spirits - "water of life" - which in Scottish and Irish Gaelic is uisge-beatha or usquebaugh. This sounded to the English ear like "uishgi" and hence "whisky". Hard though it is to admit, there is historical evidence that the water of life was first distilled on the other side of the Irish Sea. However, that does not give whiskey priority over whisky. In fact, it seems that the interpolation of the superfluous "e" was an afterthought that occurred in the 19th century. Indeed, there are extant Irish labels from the early 20th century which still use the Scottish spelling, while to this day the Canadians and distillers in Tennessee still stick by "whisky".
The good news is that earlier this year, when the Welsh restarted commercial distilling for the first time in more than 100 years, they opted for Welsh "whisky". How embarrassing for the Scot Nats that even their Welsh Celtic cohorts know the correct spelling. The SNP’s lame excuse is that an American spell-checker was being used on the office computer. But surely that implies that they typed in "whiskey", and it wasn’t underlined in red. Unlike their faces.