Prostotá (prostóy, prósto).  According to Ozhegov's dictionary (1952) it may mean: "Of uniform constitution... Uncomplicated, not difficult, easily accessible to understanding... Unsophisticated... Less than first class, of coarse quality... Good-natured, simple-minded, frank unceremonious... Completely common, in no way differing from others... Belonging to the unprivileged, exploited classes, not aristocratic (archaic [sic!])." The meaning is exceedingly complex, including the whole associative range of "simple" in English, from its positive to its negative extremes.  But the association to the "natural", and therefore unblemished, pure, powerful, rooted in the soil, is stronger than anything English can convey. Prostóy is a very common word and often used by Russians to describe themselves.