The wireless technology that is so ubiquitous in today's digital world did indeed take the name of a Viking ruler who lived more than a millennium before its creation. King Harald, reigning in the second half of the 10th century and boasted on the famous Jelling runestone of having conquered all of Denmark and Norway, was also known as “Bluetooth”.


Why was he called Harald Bluetooth?

The epithet first crops up in the Roskilde Chronicle, written in Latin in c1140. Though the source dates from after Harald’s death, there is no strong reason to question this nickname. Norse people had patronyms – the son/daughter of so-and-so – rather than surnames. (Matronyms were rare.) Nicknames were originally a common, and often creative, way of distinguishing between people who had the same or similar names.

The women Aud the Deep-Minded and Jorunn Wisdom Slope were named for their intelligence, but Ketil Flatnose and Sweyn Forkbeard for their physical features. Walking Hrolfr was too enormous for any horse to carry him, so he had to walk, while Ragnar Lothbrok’s nickname means “hairy breeches”, referring to a type of fur trousers that he wore.

“Bluetooth” likely referred to a dead tooth that had turned dark. In Old Norse, blár is used for a spectrum of blue-black colours, but also the metallic glint of armour and weapons, and even death itself, for example, in the expression “blue as hell”.

Why is Bluetooth the name of a technology?

Although being named after a dead tooth seems unsavoury, the associations between blue and weaponry or death may not have done any damage to Harald’s identity as a fearsome warrior-king.

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The software was named Bluetooth in the king’s honour, for as he united many regions into one strong kingdom, so the Bluetooth technology unites separate devices with a wireless connection.


This Q&A was taken from the April 2023 issue of BBC History Magazine


Dr Jóhanna Katrín FriðriksdóttirHistorian, author and historical consultant

Dr Jóhanna Katrín Friðriksdóttir is a medievalist, specialising in Old Norse history, literature and manuscripts. She is the author of Valkyrie: The Women of the Viking World (Bloomsbury, 2020), nominated for the Cundill History Prize