What is out of the blue?

The phrase "out of the blue" is an idiomatic expression in English used to describe something that happens unexpectedly or without any warning. It is often employed when an event or occurrence is surprising and was not preceded by any apparent cues or signals. The imagery behind the phrase suggests something emerging suddenly from a clear, blue sky, where nothing had been anticipated.

This expression is frequently used in everyday conversation to convey surprise or shock. For example, someone might say, "She called me out of the blue," meaning the call was unexpected and unprompted.

In addition to its use as an idiomatic expression, "Out of the Blue" has been used as a title in various forms of media, including music albums, songs, books, and films, implying themes of surprise, sudden change, or the unforeseen.