banging comes from bang + -ing; bang is of imitative origin, perhaps reinforced by Old Norse banga ('to hammer'). The slang sense 'excellent' is recent colloquial usage. Morphologically, the word is transparent: -ing is attached to the older base named in the history, so the modern form packages an inherited or borrowed stem inside a later English derivative. In modern use, the adjective sense is "informally excellent or very good; also a loud repeated knocking", which keeps the etymology connected to the word's present dictionary value rather than treating it as a merely historical label. The wider word family includes related English forms such as bang, showing how the same base continues to support neighboring English vocabulary. The principal historical forms in the chain include Old Norse banga, which anchor the explanation in named linguistic material.