Idiom. We all use it but do we know where it comes from?
It means: something that becomes boring after nine days. Or ceases to be a wonder, due to other events that take precedence.
Some believe it was William Kemp, a Tudor actor who morris-danced his way from London to Norwich, supposedly in nine days, and which he later called his Nine Days’ Wonder when writing of his trip. This is in doubt, as it doesn’t really encapsulate the meaning in which we use it today.
I always thought it related to Lady Jane Grey, whom Edward VI (Henry VIII’s son, who died very young, some say was poisoned) named as queen in his will, but this was overruled nine days later and she was executed in favour of Mary I. There is a lot of evidence to support this, and she is known as the “Nine days’ Queen’.
Others believe it was first mentioned by Chaucer, and yet another source cites Charles, Duke of Orleans, after the battle of Agincourt when he returned to France only to find himself a ‘nine days’ wonder’.
Maybe they all came into being independently. But whatever its origin, it is a well-used phrase, and we all know what it means. You’ve probably used it recently without even thinking about it.
Ah, the joys of English.