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

2) The term "bull market" refers to a period of rising stock prices, while a "bear market" refers to a period of falling stock prices.

3) The concept of proportional representation, used in some electoral systems, aims to ensure that political parties' representation in government aligns more closely with the proportion of votes they receive from the electorate.

4) The first graphical web browser, Mosaic, was released in 1993 and played a key role in popularizing the World Wide Web.