What technology is named after a tenth-century ruler of Denmark and Norway?

The story behind the answer

Bluetooth is named after Harald “Bluetooth” Gormsson, a 10th-century king of Denmark and Norway known for uniting warring tribes—just as Bluetooth technology unites different devices for short-range wireless communication. The name was proposed in the late 1990s by engineer Jim Kardach as a placeholder that stuck because of this apt metaphor.

A memorable detail: the Bluetooth logo combines two Viking runes—Hagall (H) and Bjarkan (B)—the initials of Harald Bluetooth—into a single bind rune. Remember it this way: Bluetooth brings gadgets together the way King Harald brought kingdoms together. In contrast, GPS, Wi‑Fi, and the Internet aren’t named after historical figures.