From Old Danish 'barlast' (bare load)—weight carried for stability alone, with no commercial value.
Heavy material placed low in a vessel to improve stability, or gravel and coarse stone used as a foundation for roads and railways.
Probably from Old Danish 'barlast,' from 'bar' (bare, mere) + 'last' (load). Ballast is literally 'bare load'—cargo that serves no commercial purpose except to weigh down the ship for stability. Key roots: bar (Old Danish: "bare, mere"), last (Old Danish: "load, cargo").
Ships arriving in America empty of cargo dumped their ballast stones on shore—many early colonial streets and buildings were constructed from European ballast stones.