puer·ile 
(pyrīl′, pwĕr-, pyər-, -əl)
(pyrīl′, pwĕr-, pyər-, -əl)adj.
1. Immature, especially in being silly or trivial; childish. See Synonyms at young.
2. Archaic Belonging to childhood; juvenile.
[Latin puerīlis, from puer, child, boy; see pau-1 in the Appendix of Indo-European roots.]
puer·ile·ly adv.
puer′ili·ty (-ĭlĭ-tē), puerile·ness (-əl-nĭs, -īl-) n.