Where did the word caucasian come from?

Everyone knows that African Americans ancestors came from Africa. Everyone knows that Asian Americans ancestors came from Asia. Everyone knows that Indian Americans come from India but really what about caucasian. I know that there are like French caucasians and German caucasians but seriously where did the word come from. Because it is very rude to call them white people so you are suppose to call them caucasians. Well actually it’s not that rude unless you are a racist person. But anyway black people are called African Americans. You see it has the African part so you know where the ancestors are from! So tell me where did caucasian come from. Is it from caucasia? Is that a place?