The document discusses the Norman Conquest of England in 1066 and its linguistic consequences. It describes how William the Conqueror, Duke of Normandy, invaded and defeated the English at the Battle of Hastings. This led to the replacement of the English aristocracy with Normans and the introduction of Old French as the new language of the ruling classes. As a result, around half of English vocabulary is derived from French, leading to "lexical doubleness" where both French-derived and Germanic-derived words exist for similar concepts.