Why is the site of a boxing match called a ring when it’s square?
The reason why boxing rings are called ‘rings’ pertains to the fact that in olden times, opponents engaged in fights within a roughly drawn circle on the ground. This ring acted as the ‘boundary’ of the fight and the fighters were supposed to contain the fight within the ring itself.
Since boxing was more of a means to settle mutual disagreements and less of a sport in those older times, the fact that there were no proper rules or laws that had to be followed during a bout isn’t all that surprising.
Whenever two people got into a fight (to settle a score or for any other reason), the viewers surrounded the two fighters. As it so happens, whenever a bunch of people stand up to see/witness an event, they invariably end up forming a circle around the event of interest (i.e., stuff that goes on in the middle).
The same thing happened in the case of boxing matches too. People tended to flock around the participants in a circle, forming a ring of sorts. Such a ring of people didn’t just unofficially define the boundaries of a fight, but on some occasions, it made sure that the fighter didn’t withdraw/run away from the fight before it was finished.
Hence, the enclosed area within which fighters fought started being referred to as ‘the ring’.