A banana plug is mainly used to insert speaker wire coming from an amplifier or receiver directly into the speaker. The banana plug is named after its shape. It is a slender, but bulging prong that is similar to a banana. However, unlike bananas, the banana plug is not bent, but straight. Other uses for the banana plug is to test electronic equipment - specifically used to terminate patch cords. It should be noted that the banana plug is the male version and the banana jack is referred to the female version of the plug.