Daily Chinese Idiom Guessing Game
To be unable to understand or explain something; baffling.
说不出其中的奥妙。指事情很奇怪，说不出道理来。
清·吴趼人《二十年目睹之怪现状》第十五回我实在是莫名其妙，我从那时得着这么一个门生，连我也不知道。”
The sudden change in his attitude was utterly inexplicable.