This plot of land, and the castle that stood here, was given to King Kenneth III of Scotland as a gift from King Edgar the Peaceful in the tenth century, and for nearly 600 years served as the residence for the Scottish monarchy whenever they visited United Kingdom.
Sorry, but... Edgar the Peaceful - what a terrifying nickname. His enemies must have been quaking in their boots. "Hide, lads! It's Edgar the Peaceful! And he's carrying flowers!"
The palace was demolished when Scotland unified with England, and a series of government buildings and residences were built in its place. Christopher Wren and John Milton each lived for a time in this neighbourhood.
When Prime Minister Robert Peel created the Metropolitan Police Service in 1829, it was decided that their headquarters would be located in this vicinity. The office's rear entrance stood on Great Scotland Yard, therefore the police force became commonly known around the world as Scotland Yard.
That the word "Great" didn't make it to Scotland Yard's nickname might be a statement of some kind. Mind you—better than just calling it "the Rear Entrance." "Come on, son—you're nicked. I'm taking you up the Rear Entrance."
The formation of Scotland Yard unified the disparate police forces that operated in different parts of London and was an instant success. By 1874, Scotland Yard employed nearly 10,000 people and expanded into several neighbouring buildings.