From Impossible to Rare: The Curious Evolution of "Once in a Blue Moon"

Language rarely travels in a straight line, and the phrase 'once in a blue moon' is a quiet testament to that truth. What began in the 16th century as an expression for the flatly impossible drifted, century by century, into a description of the merely rare — and then, in 1946, a single misreading of an almanac accidentally wrote the definition most of the world now carries. The story of the blue moon is, in the end, a story about how meaning is made not by the careful but by the many.