Originally the term referred to a design prevalent in the United States in the 1930s where front fenders encased a wheel and terminated in a teardrop point, remaining distinct from the running boards or the body of the car. Examples include the Cord 810 and 812, the Auburn Speedster and several designs by French Carrossiers, notably Figoni et Falaschi.
Subsequently the term pontoon fender took on another more prominent definition, derived from the wartime practice in Germany of adding full-length tread armor along each side of a tank, attached primarily on the top edge — and resembling pontoons. As this roughly coincided with automobile styling trend where distinct running boards and articulated fenders became less common — with cars carrying integrated front fenders and full-width, full-length bodywork — the fenders took on the "pontoon fender" nickname.
The postwar trend of the markedly round, slab-sided designs became itself known as ponton styling — with many postwar Mercedes-Benz models informally nicknamed the "Ponton".