It is a Lupearian practice that is performed during the act or art of fisting. While fisting someone's ass, the fist is opened inside the ass and moved in a spinning motion while moving the arm in and out of the ass.
It is called Cobra Fist, because it's supposed to represent a cobra wiggling up and flattening it's neck ribs to create a hood when being threatened or when snake charmer plays a flute.
It is speculated that the Cobra Fist was practiced in Rome during the times of Alexander the Great but has not been confirmed. There has also been rumors that the Cobra Fist, is part of the rituals of the Dirty Jerbear.
While the origins of the Cobra Fist is not entirely known, we do know that it is commonly practiced amongst the modern Lupearian population.
When we get back to my flat, I'm going to shock you with the Cobra Fist....
I'll cobra fist you and you will squeal like a Dirty Jerbear...