Of course mince was finely chopped/diced in the 1300's. That's hundred of years before grinders were invented. Like...I don't want to be rude but please stop and use your brain for a second on that one.

Once grinders were invented some places started calling it ground meat and some places kept calling it minced meat. But it's effectively the same thing because, like you said, back in the day they used mince for finely chopped meat, and a grinder is essentially just a mechanical way of doing that faster. Although it does also mix things together so if people these days are using mince to specifically mean finely chopped by hand then whatever. But from at least 2000-ish on every cookbook, foodie, and authority in cooking used mince and ground interchangeably to refer to ground meat, and I know that because that's when I started teaching myself to cook. The OED even has the definition of minced as to cut up or grind, especially meat, typically in a machine with revolving blades (aka a grinder).

So if people want to use mince to specifically mean ultra lean ground meat then whatever, I can see the reason for that distinction. But if you think that ground meat and mince meat have always been different things then you're just factually wrong. It's literally the same technique, a grinder is just a mechanical way of doing it.

But regardless of all that, the German dish Mett is not ultra lean ground meat and never has been. It's fairly fatty pork ground up with spices.

And in case you're wondering, the distinction between macaroon and macaron is an American thing that has since spread to different places. They're both variations of the same Italian cookie, and they used to all be called macaroons. For a long time what are now known as macarons were called French macaroons, or sometimes Parisian macaroons. At least internationally, because the French spelling of macaroon is just macaron.

But the split for the two names being used for two specific types of macaroons happened in the US around twenty years ago when they became really popular in bakeries. It was easier and more efficient to just use the French spelling of macaron for the French style cookies, and so that became the popular way to refer to them across the US and then eventually the rest of the English speaking world.