Originates from faking it, to be used when someone pretends to be more drunk than they actually are.
Did you see how pissed he was last night?
Yeh, but I reckon he was just jaking it.
He says he only pulled that minger coz he was drunk, but dont you think he's jaking it?!
Wackin it, buy if your name is jake
Person: "Hey Jake whatre you up to?"
Jake: "Leave me alone im Jaking it"