rus

From Latin rūs, rūris (the countryside, open land, as opposed to the city, urbs). The adjective rūrālis gave rural (of the countryside) and rusticus gave rustic (simple and countrified). Through French rustre, 'a boor,' rusticus also gave the lively verb roister (to celebrate noisily). Despite the look-alike spelling, it is not part of rud (rudis, rough); and rust on iron is a native Germanic word, unrelated.