language lesson of the day, from http://www.pballew.net/River.html
"The Latin origin of the word river was riparia, and represented the banks of the river instead of the water. In the Early French it became rivere, and represented both the banks and the water between them. This became the source of our modern English word, river. The current Italian descendant of the word still refers to the shore, and the Riviera is a region along the coast of the Mediterranean Sea. The older Latin version has not completely disappeared, however, and remains mostly in legal terms related to the rights of those who control the banks of the river, called riparian rights.
Closely related is the word rival, those who share a common stream. The original meaning was closer to our present word for companion, but as words have a way of doing, began to be applied to the competition that so often happens between persons seeking a common goal.
The word arrive also comes from the same root ripera. As a river bank ends when the river reaches its destination, so a journey ends when we arrive. And speaking of words that are derived from other words, derive means, literally, from the stream."