kindly in appearance but unfathomable at heart
Chinese idiom, Pinyin is h ò um à OSH ē NC í, which means that the appearance is kind and the heart is unpredictable. It's the same as "deep feeling". From Xie Xiaoe's biography.
The origin of Idioms
In the biography of Xie xiao'e written by Li Gongzuo of Tang Dynasty, "xiao'e is thick and deep in appearance, smart and special, limp in coal refining, and vows to be true."
Idiom usage
He is kind in appearance but unpredictable in heart
Analysis of Idioms
[synonym]: affectionate and profound
kindly in appearance but unfathomable at heart
vulgar or common-place point of view - shì sú zhī jiàn
a makeshift to tide over a present difficulty - wān ròu bǔ chuāng
half of the country in the southeast - dōng nán bàn bì
disappear like snow when hot water is thrown on it - rú tāng jiāo xuě