I love that www.etymonline.com has a list of trending words. Sometimes I click on them solely out of curiosity…like when I saw circus on there today.
Last May my family journeyed to Charleston, WV to attend one of the final shows of the Ringling Bros and Barnum & Bailey Circus, and it was frankly amazing. So amazing that we really wished we’d given it a try way earlier so we could have attended more and caught all their different shows. Up until then, I’d never gone to a circus, be it large or small, though a tiny little one set up once on my high school’s grounds. I saw the elephants from the road, but we had something else going on that weekend and I couldn’t go. Kinda wish I had. 
But anyway! Did you ever notice that circus looks an awful lot like circle? And circumference? And all those other circ- words that denote something round? This isn’t a coincidence. The word comes directly from Latin, where it meant “a ring, a circular line.” It was used in Ancient Rome for the open-roofed enclosures used for races and so on. The Latin word had been borrowed from the Ancient Greek kirkos, which meant the same thing.
In the early 1700s, the word was applied in English to buildings arranged in a circular pattern, hence Picadilly Circus, and also to a ring road. By the end of the 1700s, it had also been applied to the arenas used to showcase feats of horsemanship, acrobatics, etc.–but at first, it was just for the tent. It took about 40 years for it to come to mean the company or traveling show itself by 1838 or so. Another twenty years, and it had taken on the metaphorical sense of “a lively uproar, a hubbub.” And finally, during WWI, it was used to describe a squadron of aircraft.
Have you ever gone to a circus? What did you think of it?