In times long ago a ledge was happened upon. It did not seem that important at first. As there were various sizes of ledges in all sorts of places. Eventually people started to utilize ledges because they had noticed that they could lodge items on them, keeping them off the ground. Keeping things safe. We humans like safe.
A whole lot later (after all, most people are not good with change) natural ledges which had grown in popularity and had as a result become sought after and scarce were supplemented with the invention of artificial ones. We now call these artificial ledges, shelves. They were a great idea (and still are) because they allow for the lodging of things in places that were naturally lacking in ledges.
After what felt like, and actually was, an absolute age, but not as long a time as it took to get from ledge to shelf – the cupboard was invented. It was actually just a collection of shelves with a door to hide them from view. It kept items even safer than the shelf or ledge could do. Perhaps most interestingly it allowed for non-disclosure and the keeping of secrets.
A good long time after the invention of the rudimentary cupboard but not that long in comparison with progressing from ledge to shelf – the safest of cupboards – the strong box – finally arrived which kept lodged items safe as houses. So it was quickly renamed – the safe. This highly protected ledge suffered a serious disadvantage, that could not have been anticipated. It appeared to present other people with a challenge. How to get into the safe? For surely it contained undisclosed curiosities precious in nature. Breaking into safes often involved people taking risks, it forced them to go out on a ledge.