The references above on the Auchentoshan three wood are illuminating. Scotch whiskies have traditionally been matured in second-hand barrels bought from American bourbon distillers; the Septics use their barrels only once and sell them to the Scots for a cheap price. And there are plenty of them. Barrels, that is.
The last few decades the Scotch whisky distillers have started to use barrels other than bourbon to "finish" their whiskies in an attempt to revitalise interest in their products. Scotch whisky consumption has slowly decreased as our fathers pass on leaving fewer and fewer old codgers propping up the bars at golf clubs. And the ever-increasing number of cheap bourbon drinkers among the great unwashed has added to the decline of Scotch whisky. This is where interest in the Ocker Tosha 3 wood comes in: it's finished in Spanish Oloroso sherry and Pedro Ximenez casks after starting in an American bourbon one. Other distillers are now using Portuguese port, French Sauternes, Jamaican rum, Madeira, French Armagnac and other brandy casks to finish off their best whiskies. Glenfiddich, for example, use Madeira, sherry and Caribbean rum casks in their range; Balvenie have a double wood (bourbon and sherry) which was one of the few to proclaim complex multiple barrel finishing before the OT3w came along. Now it's almost de rigueur for the better malts to spend some time in a sherry cask. This modern practice of finishing good Scotch malts in exotic barrels will only become more pronounced in the future. Will a Scotch malt ever spend some time in an Australian muscat barrel? I hope so.
Interesting to note Auchentoshan is triple distilled; Irish whiskies traditionally are but very few Scotch ones go through the still three times.