Interesting sidenote. It always puzzled me why a boxing ring should be so called. Duh, it’s square! Then I found out. Nothing at all to do with the shape of the arena. Ring originally referred to the ring of spectators who would gather round to watch the prize-fighters pummel each other into raw masses of quivering flesh.
Here’s OED:
Sorry, little to do with the question, just thought I’d share it.
I’ve seen several times the explanation that before the modern age of boxing and actual rings with ropes and corners the spectators would form a ring around the boxers, or alternatively a circle would be drawn in the ground to mark where the fight was supposed to take place. I suppose you might draw that circle, but nothing would keep spectators from standing anywhere they wanted.