It's an old English pronunciation. Run down to Hampton Roads, Va. (oldest English speaking US settlement, they say... goes back 375 years anyway...) and you'll hear it, too. With a Southern twang: I don' know nuthin aboot it."
Probably wrong place to admit this, but I suffered from this misconception about the words - "Single Malt Whisky" - someone had once told me it meant something about all the malt was sprouted at the same time or ground or dried or some such thing.
It turns out it means the Whisky was produced at a single distillery, nothing more. My mind was blown by that.