Danube
The Danube was once a long-standing frontier of the Roman Empire, and today flows through 10 countries, more than any other river in the world. Originating in Germany, the Danube flows southeast for , passing through or bordering Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria, Moldova and Ukraine before draining into the Black Sea. Its drainage basin extends into nine more countries. The Danube river basin is home to fish species such as pike, zander, huchen, Wels catfish, burbot and tench. It is also home to a large diversity of carp and sturgeon, as well as salmon and trout. A few species of euryhaline fish, such as European seabass, mullet, and eel, inhabit the Danube delta and the lower portion of the river.
Danu (Irish goddess)
The etymology of the name has been a matter of much debate since the 19th century, with some earlier scholars favoring a link with the Vedic water goddess Danu, whose name is derived from the Proto-Indo-European root "*dʰenh₂-" "to run, to flow", which may also lie behind the ancient name for the river Danube, "Danuuius" – perhaps of Celtic origin, though it is also possible that it is an early Scythian loanword in Celtic.