Puerile may call to mind qualities of youth and immaturity, but the term itself is no spring chicken. On the contrary, it's been around for more than three centuries, and its predecessors in French and Latin, the adjectives puéril and puerilis, respectively, are far older. Those two terms have the same basic meaning as the English word puerile, and they both trace to the Latin noun puer, meaning "boy" or "child." Nowadays, puerile can describe the acts or utterances of an actual child, but it more often refers (usually with marked disapproval) to occurrences of childishness where adult maturity would be expected or preferred.