绵里针

Traditional (Taiwan): 綿里針

miánlizhēn ㄇㄧㄢˊ ˙ㄌㄧ ㄓㄣ

    • someone gentle on the surface but tough underneath

Character by character

Saying俗语俗語

Idiom惯用语 · Widely known

Literally
needle inside silk floss
Meaning
Describes someone gentle on the surface but firm and tough underneath. Often neutral or approving; sometimes warns of hidden sharpness.

Sources