A pedal car is a quadracycle. The Mochet Velocar seems to be the earliest example. Although originally designed for adult transportation, the popularization of motorized vehicles resulted in most modern pedal cars being made mostly for children and adult recreation.
Velocar was the name given to pedal-powered vehicles in the 1930's by Mochet et Cie, Puteaux, Seine, France. Charles Mochet was the maker of minimalist, pedal-powered cars (quadricycles), mainly two-seaters, built on a tubular-steel chassis with bicycle-sized wheels and lightweight aerodynamic bodywork. The popularity of these little cars declined as cheaper powered cars became available, only to rise rapidly when petrol became almost unobtainable during WW-2, 1939-1945.
Charles Mochet's stroke of genius was to make what was the first performance Recumbent bicycle, or vélo couché, using a design which was based on half of a Velocar.
Historically the most common layout placed the wheels at the corners of a rectangle. An alternative layout had its wheels at the angles of a rhombus (or, more generally, at the angles of a geometric kite). The rhombus layout proved less convenient, because such vehicles were less stable and left three tracks instead of two.
The first experimental steam automobiles were sometimes called steam quadricycles. The Ford Quadricycle was one of the few very early internal combustion cars called motor quadricycles. The terms automobile and car rapidly became universal, supplanting this usage.