bolt from the blue, a
Also, a bolt out of the blue. A sudden, unexpected event. For example, Bill's dropping his life insurance was a bolt from the blue for his wife. This metaphoric term alludes to totally unforeseen lightning or thunder from a cloudless (blue) sky. [First half of 1800s]
Words nearby bolt from the blue, a
bolson,
bolster,
bolt,
bolt boat,
bolt from (out of) the blue,
bolt from the blue, a,
bolt hole,
bolt upright,
bolt-action,
bolt-hole,
bolt-on