TIL radio buttons were named after the physical buttons used on older radios to select preset stations[0]. IMO they look nothing like the actual buttons on radios.
Yeah the name definitely refers more to the functionality/behavior of the buttons.
You'd push one of those buttons in to select a station and it'd stay pressed. When you push another button in to choose another station, the previously pressed button would "pop" back up/depress (thereby "unselecting" itself), thereby enforcing the mutual exclusivity of a station selection.
That wasn't anything to do with radios though. That was just the way mutually exclusive buttons worked. I had a portable tape player where the playback controls were the same way.
We have controls that mimic the actual radio buttons in the form of toggle buttons (buttons that stay depressed after pressing them), but in many APIs the programmer needs to toggle the press state of all other buttons in the group to use them.
Preset radios came in a huge variety and some of them were actually round. Car radios (the radios that have stuck around the longest) need big and bulky buttons so you can operate them without taking your eyes off the road, but some home radios had smaller, circular buttons instead.
The "radio" buttons I used as a kid were small, rectangular sticks poking out of a metal plate that you pushed in. Every brand had their own shapes and designs. Unfortunately, I can't find any pictures of older radios on the internet because every image searching site seems to have been overtaken with badly generated AI art, stock photos, and cheap, plastic "retro vintage" Amazon listings.
0: https://en.wikipedia.org/wiki/Radio_button