Blåtand

Harald Blåtand Gormsson—Harald Bluetooth—ruled Denmark from around 958 to 986 CE. The nickname Blåtand (Old Norse for 'blue tooth' or 'dark tooth') likely referred to a dead, discolored tooth. He was not a romantic figure by modern standards, but he was a unifier: he consolidated control over much of Denmark and Norway, and according to the Jelling stones—the massive runic monuments he erected in Jutland—he 'made the Danes Christian.' He brought fractious tribes under one banner.

In 1996, engineers at Ericsson, Nokia, Intel, and Toshiba were developing a short-range wireless standard to connect devices without cables. The project needed a name during a 1997 meeting in Toronto. Jim Kardach, an Intel engineer, had been reading Frans Gunnarsson's historical novel 'The Long Ships' about Harald Bluetooth. He proposed the name as a temporary codename—it captured the idea of uniting separate communication protocols the way Harald had united rival kingdoms.

The name was never supposed to stick. The consortium intended to rebrand before launch, with 'RadioWire' and 'PAN' (Personal Area Network) as frontrunners. But the launch deadline arrived before a new name was agreed upon, and Bluetooth went to market with its Viking codename intact. The logo—a runic monogram of Harald's initials, H and B in the younger futhark—has been on billions of devices ever since.

Today, Bluetooth connects headphones, keyboards, speakers, medical devices, car systems, and industrial sensors. Over 5 billion Bluetooth devices ship annually. The wireless specification that unites them all carries the name of a Viking who died around 986 CE, possibly killed by his own son Sweyn Forkbeard in a coup. The king who united Denmark was himself eventually deposed—but his name outlasted his kingdom by a thousand years.