It was on this day in 1066 that William the Conqueror of Normandy arrived on British soil. He defeated the British in the Battle of Hastings, and on Christmas Day, he was crowned King of England in Westminster Abbey.
One of the most important consequences of the Norman conquest of England was its effect on the English language. At the time, the British were speaking a combination of Saxon and Old Norse. The Normans spoke French. Over time, the languages blended, and the result was that English became a language incredibly rich in synonyms. Because the French speakers were aristocrats, the French words often became the fancy words for things. The Saxons had "house"; the Normans gave us "mansion." The Saxons had "cow"; the Normans gave us "beef." The Normans gave us "excrement," for which the Saxons had lots of four letter words.
The English language has gone on accepting additions to its vocabulary ever since the Norman invasion, and it now contains more than a million words, making it one of the most diverse languages on Earth.