The answer has to do with the year 1066, a very important year. It was the year of the Norman Conquest of England. Norman, Breton, and French soldiers led by Duke William II of Normandy, who is now know as William the Conqueror, landed in England. Actually, it was the year of the Norman Invasion. It took almost seven years before the conquest was complete. Normandy is now a part of France, and the Normans were French-speaking.
One of the many changes William made to English society was he introduced French as the language of the aristocracy and ruling class. Naturally, French also became the language of commerce, education, science, and law. The peasants spoke Anglo-Saxon, which is Old English. If you know the story of Robin Hood (Robin des Bois), the thing they never tell you is that Robin of Locksley, Maid Marian, King John, and the Sherriff of Nottingham probably all spoke French, while the Merry Men spoke Saxon. At this time, Anglo-Saxon was evolving into English and, since French was spoken by their masters, the peasants adopted many French words.
For example, in that era, the peasants were too poor to eat meat. However, their work involved looking after the animals the Normans ate. So, in modern English, our words for meat come from the French name of the animal or meat, while the name of the animal itself is the old Saxon word.
Meat Animal (French name for animal)
Beef Cow (Boeuf)
Poultry Chicken (Poulet)
Pork Pig (Porc)
Mutton Sheep (Mouton)
That is why there are so many French words in English. Since we often have two words in English for the same thing – one Saxon and one French – they have evolved to have different meanings.