French's primary influence on the English language was a result of the Norman Conquest in 1066.
When William the Conquorer took the throne of England, the French dialect spoken by the Normans became the official language of the court, administration, and eventually the culture.
This provided the English language with about 10,000 new words. Three quarters of these are still found in government, law, art, literature and food.
One weird characteristic of French we adopted was putting adjectives behind some nouns, such as attorney general, surgeon general, or secretary general.