Latin trivium is the meeting of three roads, from tri plus via, and trivialis meant commonplace, of the street corner. Separately, the medieval curriculum named its three foundation arts the trivium, with the four higher arts as the quadrivium. Modern English trivia, in the useless-knowledge sense, derives from the street meaning and was popularized in the twentieth century, notably by the 1966 Columbia University quiz contests.
A popular telling says the Romans posted news at crossroads, so trivia meant news of the junction. It is plausible and unattested; the documented path runs through commonplace, not through bulletin boards. The quiz-era revival is the one part with a paper trail.
The cutting observation: the medieval trivium was the foundation of all higher learning, and the street trivium is the foundation of pub quizzes, and English never bothered to tell them apart. High and low culture share a road junction.
We built a billion-dollar quiz industry on a word that means gutter chatter at a junction. Did the word rise, or did the quizzes sink?