I has to do with bravery, strength and the ability to endure things. In ancient times, brave young men went to war, or hunting. Now, they do things like car surfing. Think about it as a duel from 200 years ago. It didn't matter wheather you lived or died, the important part was being brave enough to accept. If not, you would loose your honor, which was a terrible thing.
If you translate that to modern times, it doesn't matter if your brother couldn't surf the car, but he tried. He would be a "chicken" if not. And it's not nice to be the chicken in a group of boys.