Is “puerile” giving boys a bad reputation? The adjective (used to describe something immature, childish, or altogether silly) comes from the Latin word “puer,” meaning “boy.” The French word “puéril” came from the Latin “puerilis,” and when “puerile” entered English in the early 16th century, it was used in the sense of “like a boy.” However, its usage evolved to describe things childishly silly and trivial — but those things aren’t limited to boys. Instead of falling back on a trite idiom such as “boys will be boys,” point out childish behavior by calling it “puerile” instead.