Even the most minimal research will show how the word “arms” was used in the 1700s.<quoted text>
"What are the inalienable and inherent rights that belong to the individual? The first and nearest one is what? The right of enjoying and defending his life. Whether he be saint or sinner, Protestant or Catholic, or what not, the first inalienable right he has, and ought to be protected in, is that of enjoying and defending his life. The next in importance is the right of worshiping Almighty God according to the dictates of his conscience. The third, the right of seeking and pursuing his safety and happiness. The fourth, the right of communicating his thought and his opinions. Fifth, the right to acquire and protect property. Sixth, the right to meet and consult with his fellows as to what will promote the common welfare. Seventh--and while enjoying all these rights, these six that I have just mentioned, he has the right to bear arms in defense of himself, his family and his state, and no man can take it away. There are seven inalienable and inherent rights of the individual man."
- Mr. C.T. Allen, Oct. 9, 1890.[Official Report of the Proceedings and Debates in the Convention, Kentucky]
In arms -- armed for war; in a state of hostility.
To arms!-- a summons to war or battle
A stand of arms -- a complete set for one soldier, as a musket, bayonet, cartridge box and belt; frequently, the musket and bayonet alone.
Under arms -- armed and equipped and in readiness for battle, or for a military parade.
It clearly refers to people going to war and never about self-defense