Ever wonder why.... ??

The more I learn about English , the more I get blur..
Can some one pls enlighten me on these.. thanks!!

1. If people from Poland are called Poles, why aren't people from Holland called Holes?
2. Why is the man who invests all your money called a broker?
3. When cheese gets its picture taken, what does it say?
4. Why is a person who plays the piano called a pianist but a person who drives a race car not called a racist?
5. Why are a wise man and a wise guy opposites?
6. Why do overlook and oversee mean opposite things?
7. Why isn't the number 11 pronounced onety one?