Bluetooth is the invention named after a medieval king, not Blu-ray, Pacemaker, or Guillotine. Bluetooth technology, developed by Ericsson in the 1990s, was named after Harald “Bluetooth” Gormsson, a medieval Danish king known for uniting various Danish tribes into a single kingdom. The name “Bluetooth” was chosen to symbolize the technology’s ability to connect and unify different devices and standards, much like how King Harald brought together various regions under his rule. While Blu-ray, Pacemaker, and Guillotine are significant inventions in their own right, it is Bluetooth that directly references a historical figure in its naming, reflecting its purpose of facilitating wireless communication and collaboration across diverse platforms.