The Scotch Game (Scotch Opening) starts with the following moves:

1. e4   e5

2. Nf3  Nc6

3. d4   exd4

4. Nxd4 (see diagram)

It dates back to 1750 when an anonymous author of Modena, Italy mentioned the characteristic opening setup in his chess treatise. However, the opening was named after a correspondence chess match between Edinburgh and London played in 1824. The Scotch Game became popular in the 19th century. At the beginning of the 20th century it fell into disfavor among top players because it was believed to release the central tension too early and allow Black to equalize without difficulty. More recently, grandmasters Garry Kasparov and Jan Timman helped re-popularize the Scotch when they used it as a surprise weapon to avoid the well-analyzed Ruy Lopez (source: Wikipedia, modified by Chris).