late 15c., from Middle French puérilité (15c.), from Latin puerilitatem (nominative puerilitas) "childishness," from puerilis "boyish, youthful; childish, trivial, silly," from puer "child, boy," from PIE *pau- (1) "few, little," with sense extended to "small, young" (cognates: Latin putus "boy," Sanskrit putrah "son, boy," Avestan puthra- "son, child;" see few, adj.).