[Latin puerīlis, from puer, child, boy; see pau-1 in Indo-European roots.] pu'er·ile·ly adv., pu'er·il'i·ty (-ĭl'ĭ-tē), pu'er·ile·ness (-əl-nĭs, -īl-) n.
1450, from M.Fr. puérilité, from L. puerilitatem (nom. puerilitas) "childishness," from puerilis "childish, boyish," from puer "child, boy," from PIE *pu- "small, little, young" (cf. Skt. putrah "son, boy," Avestan puthra- "son, child;" cf. few).