Although they might actually get it right when you tell them why it's firearm and not fireleg.
"Arms. As in weapons. In this case, a weapon that uses potent, fast burning fire to move a projectile at the speed of sound through a tube. Therefore, firearms."
"Arms. As in weapons. In this case, a weapon that uses potent, fast burning fire to move a projectile at the speed of sound through a tube. Therefore, firearms."