1959 as a shortening of monophonic in reference to recordings; earlier used among printers for "monotype machine" (c. 1925) and generally for monochrome (motorcar, etc.), 1940s. From 1964 as short for mononucleosis.
motorcar brand first marketed 1926 after merger of two earlier companies. The first part of the name, Mercedes, marketed as a car name from 1901, was chosen by Austrian manufacturer Emil Jellinek for his daughter, Mercedes (1889-1929). The Benz is from the other company, from name of Karl Benz, creator of the Benz Patent Motorwagen (1886). The surname is built from a familiar form of Berthold,
Benedict, or Bernhard.
"car which contains in itself a motor and a source of power," 1895, from auto- + car.
Which is it to be? We observe that the London Times has lent the weight of its authority to the word "autocar," which it now prints without the significant inverted commas but with a hyphen, "auto-car." We believe that the vocable originated with a journal called the Hardwareman, which succeeded in obtaining the powerful support of the Engineer for its offspring. As for ourselves, being linguistic purists, we do not care for hybrid constructions—"auto" is Greek, while "car" is Latin and Celtic. At the same time, such clumsy phrases as "horseless carriages," "mechanical road carriages," and "self-propelled vehicles" are not meeting with general favour. Why not therefore adopt the philogically sound "motor-car," which could be run into a single word, "motorcar"? [The Electrical Engineer, Dec. 20, 1895]
Compare automobile.