A “disaster” is a bad star

Before it meant catastrophe, disaster was an astrology word. It literally blamed your bad luck on the stars.

Split disaster down the middle and you get dis-, a "bad" or "wrong" prefix, plus astro, "star." A disaster is, literally, a bad star.

The etymology of “disaster”

The word came into English in the 1590s by way of Italian disastro, and the sense was pure astrology. If your life fell apart, the thinking went, it was because a planet or star had swung into a ruinous position. The heavens were against you. Your stars had gone bad.

That worldview is fossilized all over English. Being "ill-starred" is the same idea, so is thanking your "lucky stars," and calling two lovers "star-crossed" says their doom was written in the sky. We stopped believing the stars run our lives, but the vocabulary of blame stuck around.

So a disaster isn't just something terrible. It's an accusation, pointed straight up at a sky we no longer hold responsible.