It is my understanding that in many parts of the country “wh” was at one time actually pronounced inverted, as something like “hwut” for “what”. It is still pronounced that way in some regions, but not in most.
The modern English "what" comes from the Anglo-Saxon "hwaet" (meaning "Lo!" or "Listen!"... see my tagline). Even then it was pronounced "wat", with a slight aspiration before the w sound as the only reference to the h. So any dialects that pronounced "what" as "h-wut" created that sound sequence rather than reflected any original pronunciation...
Yep, exactly. It was one of the things tested for in the various Linguistic Atlas studies starting in the 1930s. If I remember right, WH was prevalent in New England and in the South. Dropping it was common in Pennsylvania and the Midland.
I believe WH has been steadily losing ground since then.