scotch is not a word a scotsman would ever use, nobody in scotland would ever describe themselves or their whisky as scotch.

I don't know if it's an english idiom (they certainly use it a lot)

but there is nothing like a scotsman ordering a whisky in london and being given jack daniels, and when pointing out that you didn't want a bourbon, they say .. oh why didn't you ask for scotch....

not to say who's wrong and who's right... but 'whisky' is scottish and 'whiskey' is irish or american

and it should NEVER be called scotch.