The meaning changing without noticing thing is interesting but not hugely surprising to me. Besides a few cartoons on TV and maybe some films, in my early life I exclusively spoke and heard British English, but with the proliferation of American English via the internet, there are a lot of words that I know full well I originally pronounced in "British", but now I'm not really sure which is the "correct" pronunciation. "Lever" and "Leverage" are good examples of words where I noticed this and had to figure out which was which. Obviously there's a difference between pronunciation and meaning, and of course I'm aware of the shift, but it feels like a similar thing.