한 이유

reason (someone) did

→ 하다

phrase Rare #17,068

reason (someone) did 한 is the past form of 하다 modifying 이유; the action being referred to is understood from the surrounding words.

KO: 그가 그렇게 말한 이유를 모르겠어요.

EN: I don't know why he said that.