Why do we say ‘once in a blue moon’? Names for the moon and other moon expressions
What’s the moon ever done for us? Well, besides giving us tides, the Islamic calendar, and a reason to celebrate 1969, it’s also influenced quite a lot of the English language. In this blog post, I’ll take a look at various sayings and moon-related words.
But, to settle us in, let’s take a quick look at the word itself. Unsurprisingly, moon has been in use for as long as English is attested. Did you know that the words moon and month have the same Germanic root? As you might have guessed, it’s because ‘month’ originally denoted the measure of time corresponding to the period of the moon’s revolution. It was only later that the new moon stopped being the starting point of a new month, and more structured months were devised – culminating, of course, in the Gregorian calendar (introduced by Pope Gregory XIII in 1582).
Then there’s lunatic – which comes from the Latin luna, the moon. Dating from Middle English, the etymology is based on the then-belief that changes of the moon caused intermittent insanity.
And if you’re the sort of person who flicks through a dictionary to find the naughty words, you might have been wondering about the use of moon to mean the buttocks, or ‘an act of exposing one’s buttocks, especially as a gesture intended to shock or insult’. Yes, it comes from the same root – presumably in the belief of some visual similarity between buttocks and the moon – and has an early use in the mid-18th century. It is much more popular in the 20th century, though, and the verb (‘to expose one’s buttocks’) doesn’t pop up until the 1960s, according to the current Oxford English Dictionary entry. Now we’ve got that out the way, let’s head on to some expressions…
Once in a blue moon
We use the phrase once in a blue moon to mean ‘very rarely’ – for example, if we say that Adam only dances once in a blue moon, we don’t mean that he never does it, but that it’s a very occasional occurrence. But did you realise that you’re conflating two earlier expressions? This particular version has been around since at least the 1830s, but once in a moon predates it by almost three centuries. It was sometimes used for ‘once a month’ (for the etymological reasons above), but also, less precisely, meant ‘occasionally’.
Meanwhile, to say that the moon is blue was used to mean something impossible – to believe that the moon was blue was to believe an absurdity. Another variant of this was to believe that the moon is made of green cheese – both these phrases can be found from the 1520s.
How did the two sayings come to be one? Well, a blue moon does exist in an astronomy calendar – ‘a second full moon in a calendar month’ – but this terminology doesn’t appear to have come into use until more than a century after once in a blue moon started being bandied about. So it seems to be simply a case of two moon-related sayings simply eliding over time.
To shoot the moon
One can shoot the moon, bolt the moon, or shove the moon, but I wouldn’t recommend doing it too often – not if you want to stay on the right side of the law. It’s slang for absconding by night – also known as ‘doing a moonlight flit’.
This terminology has been around since at least 1812, where it appears in Murphy Delany’s Feast in the unusual sentence ‘She wish’d to gammon her landlord, and likewise bolt the moon.’ The OED offers up various possible uses of gammon as a verb, though only the most charitable among us would imagine she’d planned to beat her landlord at a game of backgammon – more likely she wanted to ‘hoax, deceive, hoodwink, trick’ him.
The association of ‘moon’ and ‘month’ continues to recur in this article – and helps explain why we call the period immediately after a marriage a honeymoon. ‘The allusion’, as the OED notes, ‘may at first have been to love which wanes steadily as the moon does’, but the interpretation of love which lasts no more than a month quickly followed, if so. The word initially referred simply to the period following marriage, but since the late-18th century has most commonly been used of a holiday taken by a newly married couple – and many other languages (including French, Spanish, Italian, and Portuguese) also use the equivalent of honey and moon.
Cast beyond the moon
The moon may be one of the closer objects in space, but we’ve still adopted it as a signifier of something very far away – and, by association, something extravagant. This is seen in quite a few different expressions – to praise above the moon is to praise extravagantly; to go beyond the moon is to go to extravagant lengths. Being far away, it’s also not easy to get hold of – and to ask for the moon is to ask for the unattainable: famously, Bette Davis’s character in Now, Voyager (1942) advises her lover “Oh, Jerry, don’t let’s ask for the moon. We have the stars.” Arguably the stars are even further away than the moon, but I shan’t quibble with Bette Davis. Not again.
To cast beyond the moon, meaning to conjecture wildly, is slightly different from these other uses. I initially thought it would be symbolically referring to the casting one does in fishing – to throw the hooked and baited end of a fishing line out into the water. And this would, indeed, be rather a feat. But, in fact, this cast is the same we see in forecast – that is, ‘to calculate or conjecture as to the future’, which leads more naturally to the ‘conjecture wildly’ definition.
Over the moon
As for why we’re over the moon when happy – in earlier uses, it was to jump over the moon, signifying happiness so great that supernaturally impressive jumping for joy would be possible. The jury is still out on whether it was joy that made the cow jump over the moon – if so, the cat must be preternaturally good at the fiddle.