It origins from lol. People say lololololol (as lol many times) and sometimes they start with o, "ololololol"
The ol has been called ohl cause of the way it is pronounced.
It is also being used as nothing.
omg he's a noob, ohl.
noob1: How much have you made in your assignment
This "brain-drain" of popular, good-looking girls from high-schools is a hurdle for anyone wishing to go out with the "hot girl."
Person 2: "Sorry bud, shes going out with a guy in the OHL. You're only going to get sweet, slow hand love until you realize that hot girls only go out with guys in the O."