Head Bonking?

What happens when a brother "bonks" a brother?
You get blood.
Lots and lots of blood.
And unhappiness
And crying
And more blood
And then even later, blood
And occasionally black eyes
And bruises
And a stained shirt or two...
And then the questions...
So this is my question...When did head bonking become a deliberate, fun thing to do?
I really don't like it when I accidentally bonk heads with someone,
it hurts,
I see stars,
and sometimes the room spins around.
But to intentionally bonk heads for fun?
Hmmmmm......makes me wonder if I am missing out on something.
I haven't yet figured it out.