推荐 Word Power Made Easy 这本书，深入浅出讲解词源。Trivial 在第 215 页有讲。

“Surprisingly, via, road, is the root in the English word trivial
(tri-, three). Where three roads intersect, you are likely to find
busy traffic, lots of people, in short a fairly public place, so you
are not going to talk of important or confidential matters, lest you
be overheard. You will, instead, talk of trivial things
-whatever is unimportant, without great significance; you will
confine your conversation to trivialities or to
trivia (also a plural noun), insignificant
trifles. ”