Why so mysterious?Are you hiding something from me?

干嘛神秘兮兮的？你有事情瞒着我吗？

youdao

Why are you so mysterious? Why don't you tell me outright?

你为什么这么神神秘秘？为什么不直截了当地告诉我？

《柯林斯英汉双解大词典》

Along with the long cultural history of dream analysis, their apparently mysterious source may be partly why some people find dreams so influential.

伴随着析梦的长期文化史，梦的神秘渊源可能是为什么有些人认为梦具有如此的有影响力。

youdao

Exactly why a glass door on a refrigerator would be so appealing is kind of mysterious.

FORBES: The Sub-Zero PRO 48 puts the cool in cold storage.