If something happens out of the blue, it happens suddenly and with no warning at all. A letter arrives out of the blue from someone you last saw twenty years ago; a company announces redundancies out of the blue. The ‘blue’ is the clear blue sky, and the thing left unsaid is the thunderbolt that falls from it.
What’s the origin of the phrase ‘out of the blue’?
The phrase is a clipped version of ‘a bolt from the blue’, which likens a sudden event to a thunderbolt out of a cloudless sky. The earliest known appearance of the longer form in English is in Thomas Carlyle’s history The French Revolution, 1837. Describing the arrest of Hébert and his fellow radicals in March 1794, Carlyle wrote:
“Arrestment, sudden really as a bolt out of the Blue, has hit strange victims.”
The picture itself is much older. Horace, in his Odes (Book 1, 34), describes Jupiter driving his thundering horses and chariot through a clear sky (‘per purum’), and claims the shock of it frightened him back into religion. Carlyle was a classically educated man and would have known the passage, though whether it was in his mind when he wrote we can’t say.
Victorian journalists took the bolt image up enthusiastically. The Standard (London) reached for it in August 1863: “This is verily ‘a bolt out of the blue’”, the quotation marks and the paper’s added gloss (the lightning flash in a sunny sky) suggesting that readers still needed the figure explained. By the time The Dundee Courier reported a Commons surprise in April 1875 (“A bolt out of the blue struck this afternoon. Nothing calmer than the Parliamentary sky could be imagined”), no explanation was thought necessary.
Towards the end of the century the bolt started to drop away. The earliest example yet found of plain ‘out of the blue’ is from The Spectator of 22nd February 1879, in a piece puzzling over The Times’s coverage of India:
“Twice this week, the organ of her Majesty’s Government has fired off articles so completely ‘out of the blue’ that it is difficult to believe they are uninspired.”
Again the quotation marks: the writer clearly felt the phrase as a borrowed figure rather than plain English. That feeling didn’t last. Over the twentieth century ‘out of the blue’ became the standard everyday form, while ‘a bolt from the blue’ survives as the more formal and more vivid original. Fuller wordings that spell out the image were common on both sides of the Atlantic; ‘out of a clear blue sky’ is still heard, and a Gettysburg newspaper had ‘like a clap of thunder out of a clear sky’ as early as 1836.