I found this article about icons to be interesting.

The article provides some background about the original design of these now-common icons.

One of the things that doesn’t isn’t brought up the article is how people process icons. A good icon does not necessarily have to be immediately intuitive. More importantly, an icon should be easily recognizable. The first time you use an icon you may need some guidance as to what it represents. But from that point onward, it is merely a an image/object no different from a right-facing arrow. We recognize a right-facing arrow because it is so well known. But it had to become known at some point by every one of us.

It certainly helps if an icon maps in some way to our existing mental models of things. But that is always difficult to do in a small amount of screen real estate. And a literal representation does not necessarily translate between languages/cultures.

As professionals who use icons, we want to choose the ones that appear to have the most reach within our intended audience. If we are creating an icon from scratch or using an unfamiliar icon, we may need to have some form of Help text associated with it. In a mouse GUI, this could be a tooltip. In a touch interface, it might require an overlay or Help text triggered by a touch and hold.