Lead has had a great multitude of uses throughout history. The ancient Romans pioneered the use of lead in coins, utensils, and all manner of plumbing. It is for this last fact that the symbol Pb and the word plumbing share the same Latin root: plumbum. The metal was useful in ancient times because it was soft and plentiful in mines near the surface. Closer to modern times lead was used in shoes, lightbulbs, toys and most importantly paints (as illustrated by the Dutch Boy's Lead Paint company's coloring book top left) because of its various unique properties in mixtures. However the most profound impact lead had on the 20th century was its use in the compound Tetraethyllead (CH3CH2)4Pb invented by Thomas Midgley Jr, which, when combined with gasoline, reduced engine "knocking" and improved fuel economy and engine performance in cars. The ball-and=stick model of Tetraethyllead is shown at the top right.