I might have forgotten it, if you hadn’t pointed out that it actually can be seen. Don’t know what it looks like, but there is another one that can be seen, so I took that;)
They are called universal joints in English (didn’t know that…) and they are indeed beautiful when animated!
There are a few tutorials on how to rig these things, I haven’t seen all, but I liked this one: https://www.youtube.com/watch?v=cUC3W_rW7dc
