Umber is a dark brown or reddish-brown pigment that is found in certain minerals. Ever since humans started creating art, they've been using umber.
Pigments are the shades of color that painters and other artists use, and when they occur naturally, they're called earth pigments. Umber falls into this category — its rich, deep brown shade comes directly from minerals (raw umber) or from minerals heated to a darker shade (burnt umber). Today, oil painters still use umber when they need a fast-drying brown pigment. Umber gets its name from a region in Italy where it's common, Umbria.