Harald Bluetooth was a Viking king who ruled Denmark and parts of Norway during the late 10th century. He is best known for uniting the various tribes of Denmark and converting them to Christianity, which helped to establish a more centralized kingdom. His reign marked a significant transition from paganism to Christianity in Scandinavia. The name "Bluetooth" is derived from Harald's nickname, which refers to his penchant for eating blueberries. Today, the term is also associated with wireless technology, as the Bluetooth standard was named in his honor, symbolizing the connection of devices much like Harald connected different tribes under his rule.