穿开裆裤

Traditional (Taiwan): 穿開襠褲

chuānkāidāngkù ㄔㄨㄢ ㄎㄞ ㄉㄤ ㄎㄨˋ

    • to be a small child
    • to be young and ignorant

Character by character

Saying俗语俗語

Idiom惯用语 · Widely known

Literally
wear open-crotch trousers
Meaning
To be a small child, and so young and ignorant. Often said of someone's childhood ('since we wore split pants') or to dismiss someone as naive.

Sources