When you think of Pluto, you probably assume it was named by astronomers. Given that it's the most recently discovered planet — found in 1930 — you might think it was named to fit the existing scheme, in which all the planets were named after Greek or Roman gods.
You'd be wrong. The name was first suggested on a whim by a 12-year-old girl during breakfast.
That girl would be Venetia Burney, the British schoolgirl who came up with it in March 1930, shortly after the planet was discovered. Burney died in 2009 — so she won't be able to see the New Horizon probe make the first-ever flyby of Pluto next week — but she told the story to NASA in 2006, when the probe was launched:
I was having breakfast with my mother and my grandfather. And my grandfather read out at breakfast the great news and said he wondered what it would be called. And for some reason, I after a short pause, said, "Why not call it Pluto?" I did know, I was fairly familiar with Greek and Roman legends from various children's books that I had read, and of course I did know about the solar system and the names the other planets have. And so I suppose I just thought that this was a name that hadn't been used.
How Burney's suggestion became Pluto's official name
For decades, astronomers had searched for a hypothetical "Planet X" beyond Neptune, but when Clyde Tombaugh found it in February 1930, he and colleagues at Arizona's Lowell Observatory didn't have a name in mind.
After the discovery, they received dozens of suggestions from all over the world — including Pluto, which came by way of Burney's grandfather, the prominent Oxford librarian Falconer Madan. He passed it along to Oxford astronomer Herbert Hall Turner, who sent a telegraph to Lowell Observatory that read "Naming new planet, please consider PLUTO, suggested by small girl Venetia Burney for dark and gloomy planet."
The astronomers eventually put it to a vote between Pluto, Minerva, and Cronus. In May, it was announced that Pluto had unanimously won. Roger Lowell Putnam, trustee of the observatory, explained the choice to the New York Times:
The discovery of this planet is so pre-eminently a triumph of reasoning that Minerva, the goddess of wisdom, would have been our choice if her name had not for so many years been borne by an asteroid.
Cronus, the son of Uranus and the father of Neptune, would have been appropriate, but so is Pluto, the god of the regions of darkness where Planet X holds sway.
It also helped that Pluto began with the letters P and L — an homage to Percival Lowell, the founder of the observatory and the originator of the search for Pluto.
Burney said she'd essentially forgotten about the whole idea in the intervening months and was delighted to hear that her suggestion had won. Her proud grandfather gave her a £5 note as a reward.
Burney went on to work as a math and economics teacher for decades and lived to the age of 90 — just long enough to see a tiny spacecraft named New Horizons launch to Pluto 76 years after she'd named the planet. "It is absolutely amazing," she told NASA at the time. "We have stepped so far into the future as it were since the 1920's and 1930's. It leaves one absolutely stunned."