I'll admit, I didn't know the Supreme Court had said that.

It's an insane interpretation - and I see that many justices said so at the time.

I guess whether or not the writers of the amendment actually meant every able-bodied man when they wrote "well-regulated militia", or whether they meant a militia, is impossible to know for sure.

But to say that the word meant something different at the time is patently untrue. Around the English speaking world at that time, local militias - with that specific word used - were used to keep order. It was a common word for an actual thing people would have been familiar with.