Why do English and French share so many words?

English and French share so many words mainly because, after the Norman Conquest of 1066, French became the language of England's rulers for centuries. William of Normandy, Guillaume le Conquérant, took the English throne, and his Norman French replaced English at court, among the aristocracy, in the law courts and in the Church. Ordinary people kept speaking English, but anyone dealing with power had to use French words.

Those words stayed. Estimates of the share of English vocabulary that comes from French range from a third to two thirds, and law alone gave English justice, crime, jury, pardon, arrest and evidence. The peak came between 1250 and 1400, when 40% of all the French words in English first appear. Even word-building pieces crossed the Channel: suffixes like -tion, -ment and -able.

There are fun oddities. Some words were borrowed twice, once from Norman and once from Parisian French, which is why English has both catch and chase, warranty and guarantee. And beware of a famous story: that English peasants raised cows, sheep and pigs while French-speaking nobles ate beef, mutton and pork. Walter Scott popularized it in Ivanhoe, but the French food words appeared around 1300 and long named both the animal and its meat. The neat split came centuries later.