1) The name "Bluetooth" comes from the 10th-century Danish king, Harald Bluetooth, who united Denmark and Norway.

2) The concept of sovereignty refers to the supreme authority and power of a state to govern itself, make decisions, and control its own territory without interference from external forces.

3) The Russian Revolution in 1917 resulted in the overthrow of the monarchy and the establishment of a communist government under Vladimir Lenin.

4) The first video game console, the Magnavox Odyssey, was released in 1972 and featured games such as Pong and Table Tennis.