There is a Chinese buzzword called "闷骚" (mēn sāo). It refers to people who look quiet, cold or even dull outside, but inside they are volatile, charismatic, hot and sexy. It may also be used to describe a person's duplicitous personality, but mostly in the eulogistic sense. Someone translated it into "surprise package." I'm wondering if there is another common used phrase for it in English-speaking countries.
I can't think of an expression that directly applies as a noun phrase for this type of person. May I suggest some phrases that refer to or describe a person to see if they convey the same idea?
Possible the expression "he/she is like a smoldering ember", it indicates a person who has the potential for passionate feeling or action but has not yet burst into flame.
The other term that comes to mind is "still waters run deep" which implies that people who are quiet and don't try to attract attention are often more interesting than people who do try to get attention.
Are we "beating around the bush" here? Does this Chinese expression refer specifically to a hidden sexual passion? Some of the responses seem to indicate this. Or can this be a hidden passion of any kind?
You have a good guess! In some cases, it does refer to a hidden (sexual) passion, but not very specifically.
So it seems that "still waters run deep" is the very phrase to describe a "闷骚" person.
这么看来很难找到一个能完全形容“闷骚”的固定英语短语。最接近的短语也只能是“Still waters run deep(静水流深/大智若愚)”了。