The term "banding-balls" refers to a specific type of bondage or kink play that involves tying or binding the testicles of one or both participants. This can be done using various materials such as ropes, straps, or other restraints.
In a porn video context, banding-balls is usually associated with BDSM or kink scenes where one partner is in control and the other is receiving pleasure or pain from the action. The purpose of this act can vary, ranging from simple sensory deprivation to more intense forms of domination and submission.
The term itself combines two concepts: "banding" refers to tying or binding, while "balls" obviously points towards the testicles. So, when you see the tag "banding-balls," it is indicating a scene where the testicles are bound or tied in some manner.