One of James Madison's fears about the Constitution was, he knew that over time, the meaning of words changed.
To the men of his time "well regulated" simply meant well trained, or, well disciplined.
Don't let anyone tell you that it means that the government can dump a truck load of "regulations" on it like they do now. Back then, the government had VERY LITTLE to say about anything!
.".....that whensoever the general government assumes undelegated powers, its acts are unauthoritative, void, and of no force....."
-Thomas Jefferson,Kentucky Resolutions of 1798