Meaning

noun a young person, not fully developed

adjective of or relating to or characteristic of or appropriate for children or young people

adjective displaying or suggesting a lack of maturity

originBorrowed from Latin iuvenīlis (“youthful; juvenile”), from iuvenis (“young; a youth”) + -īlis (suffix forming adjectives indicating a relationship or a pertaining to). Iuvenis is ultimately derived from Proto-Indo-European *h₂yuh₁en- (“young”), from *h₂óyu (“long life; lifetime”) (from *h₂ey- (“age; life”)) + *h₁én (“in”).

Etymology from Wiktionary, CC BY-SA 3.0