bolt from the blue, a

A sudden, unexpected event, usually of a cata- strophic nature. The term refers to a bolt of lightning or thunder that comes from a blue (cloudless) sky and hence is not anticipated. Although “blue” was a poetic allusion to the sky by 1700, the precise expression dates from the early nineteenth century. It appears in Thomas Carlyle’s description of chaotic events of the French Revolution: “Arrestment, sudden really as a bolt out of the blue, has hit strange victims” (1837).