For example, in the Middle Ages people believed that when someone sneezed their soul came out of their body until they inhaled again. During that crucial moment an evil spirit might get in and possess the sneezer unless someone said, "God bless you."
A lot of our manners are based on war.
We no longer kneel or bow except in limited situations. Back then bowing was a way of showing submission and trust because doing so gave another person the opportunity to attack the one who was bending over by hitting them on the head or even cutting it off .
Knights in armor wore helmets, and removing them was a sign that they were not intending to defend themselves. That's why men removed, or later tipped, their hats when meeting a lady or a man they respected, or entering a church or the home of a friend.
But even homes were not always safe places in those days. When tables were set a sharp knife was placed on the side near the right hand, which was dominant for most people. The knife was used for cutting food, but available in case a fight broke out.
And men would extend, join, and shake their right hands to show that they weren't going to use a weapon.
Even saying "Please," which is short for the phrase, "If you please," showed submission because people in positions of power would simply command others to obey them while everyone needed to ask equal and superior people if they were willing to do something.
Although most people aren't aware of the origins of such traditional behaviors we still do them. I wonder how much longer things like that will continue to be used in our culture.