Everyone knows the Bluetooth logo because everyone has to used it to make their speakers work or whatever.
You might already have known that Bluetooth was named after a Viking king, Harald Blåtand, or "Harold Bluetooth".
Blåtand was the first Christian king of Denmark. He was born some time around 935 CE and ruled between roughly 958 and 986.
But it's even cooler than that. The Bluetooth logo itself is made of two Viking runes, spelling out Harald's initials.
You can read more about it in this Smithsonian article, which is where the Red Dwarf Science Twitter account got its information.
Harald was apparently a great communicator, which is how he converted Denmark to Christianity.
And here's Harald himself, completely unaware that a thousand years after his death he would be remembered as a way of tethering your phone to your tablet so you can use the internet on the train.
Thank you, Harald!
Tom Chivers is a science writer for BuzzFeed and is based in London.
Contact Tom Chivers at email@example.com.
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