“
The Danube, first recorded as the Danuvius, was named after the Celtic goddess Danu, whose name means “divine waters”. The Rhône, first recorded as Rhodanus, also incorporates the name of the goddess prefixed by the Celtic ro, or “great”. The Rhine, originally recorded as Rhenus, is a Celtic word for “sea way”.
”
”
Peter Berresford Ellis (The Mammoth Book of Celtic Myths and Legends (Mammoth Books 196))