When I was a little kid, maybe 5 or 6 years old, I was riding along in the car with my Grandma and we passed a golf course. Grandma rolled down her window and shouted, "Fore!"
This confused Little Jamey, who asked, "Why did you yell 'four,' Grandma?"
I don't recall her exact answer but it was something like, "Because that's what you do when you play golf."
Of course, this was an oversimplification, but it sounded good at the time, and looking back on it, I suspect Grandma just wanted to see some golfers duck for no good reason. (Which, if you think about it, is plenty of good reason.)
Anyway, ever since he was little, I've told my nephew to yell "Fore!" whenever we pass a golf course. Because everyone needs a little tradition in their lives and we're feisty like that.