What I mean is like for example, a person having “gravitational pull” or someone making a “quantum leap” makes no sense to anyone who knows about physics. Gravity is extremely weak and quantum leaps are tiny.
Or “David versus Goliath” to describe a huge underdoge makes no sense to anyone who knows about history, because nobody bringing a gun to a sword fight is going to be the underdog but that’s essentially what David did.
I’m looking for more examples like that.
I don’t know about ancient duel rules to say whether bringing a sling was permitted. The take is more along the lines of “David wasn’t an underdog. If anything, David was the clear favourite to win because of his weapon”. Because a sling at the time was a highly effective and deadly weapon which was still regularly used for centuries after the supposed events of that biblical story because of its effectiveness.
It was simply a war, and no rules.