Here’s an unimportant question for you: What is a single word for the intersection of three roads? The answer: trivium. Now, pluralize the word in the Latin way, and you’ll have another bit of non-useful information: trivia.

Although trivia began as a geographical term, it came to denote the inconsequential information people exchange when bumping into each other at a trivium—bits of gossip or news that keep conversation short, cordial and interesting. In other situations, these trivialities became evidence of mental virtuosity, scraps extracted on demand from the vast store of data people carry around with them. Because some people seem to possess more facts than others—and readier access to them—a mental sport was born in pubs and living rooms everywhere. Contestants gleeful...