People use the word “once in a blue moon” to describe something that almost never happens. We think it’s synonymous with “rare”. However, its original meaning was much more dramatic. It meant impossible.
This change did not happen overnight. Its history goes back to the 16th century. At that time there was a saying: “The moon is blue.” A lie. Something that could not be true.
In 1883, nature intervened. The Krakatoa volcano in Indonesia exploded. It was one of the most violent volcanic eruptions ever. Volcanic ash is not limited to Indonesia. It circled the globe.
For two years after the explosion, the sunsets took on strange colors. People report seeing a blue moon. It wasn’t a metaphor. It was a physical reality caused by atmospheric particles. The ash filtered sunlight and reflected blue wavelengths.
The event was possible. Just uncommon.
As the world adjusted to this new reality, this idiom changed as well. “Once in a lifetime” no longer means “never”. Originally it meant “very rare”. We lose track of what is impossible. We feel a sense of scarcity.
The shift from “impossible” to “rare” brings about a big change in the way we express the extraordinary.
when you say you’ll see a blue moon, you’re not predicting a miracle. You are expecting something rare. These words now carry the weight of volcanic ash. Not just old superstition.