Taupe refers to a dark grayish-brown color. The word "taupe" derives from the Latin name for the European Mole, Talpa europaea.
Originally, this referred only to the average color of the French mole, but like the colors pink and lavender, the name expanded (in the case of taupe beginning in the 1940s) to encompass a wide range of varying shades. It seems that this occurred because the color of the fur of the mole can itself be a wide range of shades, from gray through yellowish, brownish, and even purplish.
The first use of taupe as a color name in English was in the early 1800s (exact year is not known).