Word History: The Don River in Mother Russia is well known, as are the unruly Cossacks who dwelt there, defying khan and czar. But there are also six Don Rivers in the United Kingdom! Were there Cossacks in Shropshire? Hardly. All these Don Rivers flow from one Indo-European source. The Indo-European root *dā- means "to flow, flowing," and its suffixed derivative *dānu- means "river." In Avestan, the earliest Iranian language we know, dānu- means "river, stream." In modern Ossetic (the language of the Ossets, descendants of the Scythians, an Iranian tribe of the Russian steppes), don means "river, stream." The Don River of Russia (and the UK) therefore simply translates as "the River River." The Russian rivers Dnieper and Dniester (earlier Danapris and Danastius, respectively) come from Scythian Dānu apara and Dānu nazdya ("the river in the rear" and "the river in front," respectively). The six Don rivers in Britain come from the Celtic version of the "river" word, also dānu-. This survives more or less intact in the name of the Danube, which was called Dānuvius by the Romans. The presence of Celtic river names both in Britain and in central Europe attests to the Celts' earlier glory as one of the most important peoples of ancient Europe. Tatar Duna ancient Tanais. River, southwestern Russia. Rising south of Moscow in the central Russian uplands, it flows generally south for 1,162 mi (1,870 km) to enter the Gulf of Taganrog in the Sea of Azov. In its middle course it flows into the Tsimlyansk Reservoir, which dominates the Don's lower course. Most of its basin is rich farmland and timberland. A major shipping artery, it is navigable (in the spring) as far as 990 mi (1,584 km) from the Sea of Azov