Did these buttons first show up on cassette players? The reel-to-reels I can think of had multi-position switches.
This machine is apparently from 1961, so it must have been quite early in the 60s: http://www.reelprosoundguys.com/images/1962_GRUNDIG_TK_46.jp...
Here's an interesting reddit discussion about it with an image of an older style play button.
And an older more in depth discussion on the same thing
For a very basic and obvious example, possibility to turn right vs turn left signs look different not just because of convention but they resemble the shape of the road.
One thing to be aware of with both names and logos, is potentially what the name/logo may mean in other places throughout the world.
To go further with the idea of context, a square on its own is meaningless, a square next to a circle and a triangle means stop, next to play and record.
And it's also these relationships that will tell the user what to click on.
If you're designing a B&W icon set, at least make sure that each one has a very eye-catchinge, different outline.
Too many icons now are monochrome squiggles and blobs on a (rounded) rectangle silhouette. About as horrible as it can get.
Most of the time text would be more useful than iconography. Even when you don't understand the language, text and iconography are about the same - some squiggly lines that mean nothing, that you have to attach meaning to.
There are a bunch of people that studied semiology of graphics. Frutiger did a lot of work in iconography. Vignilli and a few other
PS - Btw, skeumorphic design is back, watch out for it in the next decade.
The point about Houdini, Max, and Solidworks needing deep training is ridiculous, a French horn only has 3 or 4 keys, so all players should be able to achieve proficiency easily. However in music, (and 3D modeling) deeper concepts exist to create meaningful and diverse compositions.
(1) Icons are a recently modern idea - the 1964 Tokyo Olympics employed them to bridge language barriers. Today icons/pictographs are used in almost every interface and wayfinding (signage) device around the world.
Skeuomorphic design is a good concept to help users understand general concepts. Advanced users who have a grasp of computing are more apt to interpret abstract icons and use them as time savers.
I think it was seen as cool for some people to talk negatively about skeuo, because it brought clicks. Most of these blogposts criticizing skeuomorphism never understood what it was about at first place, and it has nothing to do with how much bevel/emboss or drop shadow a UI has. Realword users like skeumorphism because they want some familiar UI, not some abstract/minimal thing that looks good only in Dribbble...
Try sitting someone who has never seen your UI before down in front of it, and try to explain to them how to do something without pointing at the screen, and see how much they struggle if your buttons only have icons.
It's unfortunate that many designers these days often jump for hamburgers and heiroglyphs in circumstances where that sacrifice doesn't make sense.
The most important part about the car icons is the color: an orange icon means you can go, a red icon means you must immediately stop.
There are lots of ways to do it. You could just include a page in the manual: "These icons indicate emergencies. Those other icons are just warnings," and expect color-blind users to memorize it. It's not optimal, but it's better than nothing.
Emergency icons might be larger, or perhaps flash (gently). You could include a octagonal stop-sign border around icons that indicate emergencies.
Using color as an additional channel for the 90+% of people in the world who can see it. But the remaining set (over 10% of men) are a sizeable audience.
hope i did convey the idea.
edit: You should probably use a icon like this one https://www.iconfinder.com/icons/830113/character_figure_man... for the person instead the one i linked, since showing only the head instead of the entire body is not very clear (i used that one only for explain the emblem idea)
But even without the text it still has some problems, since without context you may think it mean body hydratation level or blood, unless you use colors (yellow, blue and red ) to distinguish between them, but even then, they are not always available/possible and pose accessibility problems, for visually impaired (is the correct word?) etc...
you could also use the text, if you target a specific locale, or also localizing the icons may make sense.
Since i don't know where this icons will be used i don't know what the best solution and i don't have a perfect solution.
I hope I have explained myself better.
The context is for a fitness app.
Why .cc? I guess because it's familiar-ish. It's easy to hit the "c" twice, and "c" is the first letter of "com".
In this case, uxdesign.com refers to a blog that has lain fallow for a decade. It does no harm sitting there, and it may as well as long as its owner remembers to pay the trivial sum to renew it. But "uxdesign" might as well get new life in some other TLD.
Clear, quite colorful, and they communicate the spell function well. In the worst case, they're easy to memorize. I still like the black&yellow style.
HOMM1 is also good.
Heroes of Might and Magic 3 made them more decorative, but they're still clear:
HOMMIV spells - what do these do?
Might and Magic Heroes 5 - you need an art historian to figure these out.