Meaning/Usage: Out of nowhere; spontaneously(莫名其妙的,不由自主地)
Explanation: Although "blue" represents being sad, it is also commonly used to represent the ocean or the sky. Both are extremely big. If someone says to look for something that is in the sky or the ocean, there is no way to know where. Therefore, this phrase was created to represent coming out of nowhere.
"He's pretty funny because he will crack a funny jokeout of the blue."
"Grace started crying for no reason. It was totallyout of the blue."
"I don't know why he started getting mad. It wasout of the blue."
A: "Did you hear what happened with Tiffany?"
B: "She broke up with her boyfriend last night."
A: "What? I thought they had a great relationship."
B: "So did I. It was totallyout of the blue."
Other Common Sentences
"She showed up out of no where."
"He pulled a rabbit out of nowhere. That's why it was so impressive."