childish
adj.
Old English cildisc "proper to a child;" see child + -ish. Meaning "puerile, immature, like a child" in a bad sense is from early 15c. Related: Childishly; childishness.
〔李〕[child n. 小孩；-ish →] a. like a child；immature；fool-ish孩子气的；幼稚的；傻气的