out of the blue
Meaning: If something happens out of the blue, you're not expecting it to happen and you're surprised when it does.
- A letter came today, totally out of the blue, from a lawyer who said that an uncle I hadn't heard from in years had died and left me a million dollars. But then my alarm went off ... and I woke up.
- A girl Barry had known years ago called him out of the blue and invited him to her wedding. He was very surprised, as you can imagine.
The economic crash came out of the blue. Nobody