[NWoodsman]

Historically military slang referred to the “regulars” which was the way to say “they guys you call upon to get dirty” and would mean different things depending on the army… a British regular would be a redcoat conscript, a US regular would be a militia volunteer from one of the colonies.

Guns were not issued to citizens, but were owned personally. It makes sense that the resulting law would read “we want the ability to have a militia and have those guys bring along their guns”. Especially because there was no standing army at the time, it was envisioned that the US Army was simply a way to refer to a conglomeration of state militias, not an organized Army.