American Lexicon Gobsmacked

[xela]

I heard a middle class American man in his sixties use the word "gobsmacked" in a sentence today. It's been less than two years, perhaps less than one, since the first time I heard an American use it in some context other than mentioning it as something Brits say. Now it's part of the lexicon of mainstream speakers of American English. I'm assuming it's been assimilated so rapidly because so many people have heard in in the Harry Potter movies, so the first time they hear it from a live speaker the ground is already prepared.