Many cultures over the centuries have used and use gestures to usually express a feeling.
One of the oldest gestures is the one showing the extended middle finger on the back of a closed fist, which mainly symbolizes contempt for the person being addressed. At the same time it implies urging for someone to “get fucked”.
The middle finger symbolizes the penis and the curved fingers on each side of it the two testicles.
The extended “middle finger” comes from ancient Greece, where the gesture was used as a symbol of anal contact in a way to degrade, intimidate and threaten the person to whom it was addressed.