We use today many expressions the meanings of which are clear enough, but whose literal meaning may be lost — at least we don’t think about it. This is because a lot of them originated decades or centuries ago. (Don’t take it amiss if I am telling you something you already know — you’ll find the origins interesting to recall.)
The metaphorical expression “a flash in the pan” is commonly used today to describe some event which is momentarily exciting, but whose interest or effect quickly disappears from the scene. This idiom comes from the days of the flintlock, or perhaps even its predecessor the matchlock. In those days you fired your musket by putting powder in the priming pan next to a small hole drilled through the barrel. This hole allowed fire from the gunpowder in the pan to ignite the powder charge that propelled the musket ball. If the flint ignited the powder in the pan but the weapon did not fire, you had only the “flash in the pan” — bright and colorful but ineffective.
You also had to “keep your powder dry,” although how in the world that could be done in the pouring rain I’ve never figured out. You would probably often want to chuck your musket into the river, “lock, stock, and barrel — “ except in a battle you’d in probably need the backup bayonet (which got its name centuries ago from Bayonne, France — no, not New Jersey — where it was invented). Speaking of musket-chucking, the Germans have a nice phrase for “throw in the towel.” Someone who quits or gives up “wirft die Flinte gleich ins Korn” — he “throws the musket into the cornfield.”
I think “kick over the traces” is still occasionally used to describe someone who leaves his job and family and heads for California on his Harley, although it may be that I am the only surviving user. It means to rebel against the conventional rules of behavior, doing what you want and thumbing your nose at authority. The “traces” were long pieces of leather that joined a vehicle to the horse pulling it. A horse “kicking over the traces” kicks its legs over these pieces of leather and goes out of control, scorning the equine proprieties. “Thumbing your nose,” incidentally, goes back at least to the time of Shakespeare.