Bluetooth is a standard for short-range wireless communication between various electronic devices including keyboards, computers, laptops, PDAs, smartphones and many others. ¹⁾

It has a Danish king's name. Harold 'Blåtand' Gormsson, the 10th century King of Denmark, enjoyed blueberries so much that his teeth were blue forever. The “Bluetooth” version of his username is clearly anglicized. ²⁾