When you decide to crash at a party and are either;
a) Far too drunk to find yourself a blanket to cover yourself with
b) The awkward stranger who nobody knows at the party and doesn't GET a blanket
c) The only one without a blanket.
So due to lack of blanket, you use your coat for pathetic warmth. Blanket+Coat=Clanket
Drunk Chick: Gurrrrl, I'm about tah fall asleep up in this corner on the hardwood floor, I'm too wasted to get home. You got a blanket ah can useeee?
Irritated Drunk Chick Who Regrets Throwing Party: No. I'm out. Clanket it, bitch.