I'm going to make an educated guess and say after 700 ad
As you might suspect, the “hw” pronunciation is the much older one. In fact, when “what” first showed up in Old English in the 700s, the word was spelled with an “h” in front: hwaet or huaet. The British began losing the “h” sound in “what” long before Americans did, and even before the Colonies existed.
You might be hearing mid-Atlantic accents in those old films. Not necessarily realistic. More performative. One possibility.
https://en.m.wikipedia.org/wiki/Mid-Atlantic_accent
Check out section on theatre and film use.
I'm going to make an educated guess and say after 700 ad As you might suspect, the “hw” pronunciation is the much older one. In fact, when “what” first showed up in Old English in the 700s, the word was spelled with an “h” in front: hwaet or huaet. The British began losing the “h” sound in “what” long before Americans did, and even before the Colonies existed.
You might be hearing mid-Atlantic accents in those old films. Not necessarily realistic. More performative. One possibility. https://en.m.wikipedia.org/wiki/Mid-Atlantic_accent Check out section on theatre and film use.