不知何故

bùzhīhégù
somehow

CEDICT

不晓得什麽原因。

重編國語辭典

Entry Composition

1 不知 bùzhī
  1. not to know
  2. unaware
  3. unknowingly
  4. fig. not to admit (defeat, hardships, tiredness etc)
2 何故 hégù
  1. what for?
  2. what's the reason?