THE MEANING OF CUSH BY THE RIVER.

Genesis 2:13: "And the name of the 2nd river is Gih'On, the same name is it that encompasses the whole land of Ethiopia."
Ethiopia is a well known kingdom, and a country in which one of the sources of the Nile River lies. The Blue Nile rises in the Ethiopian mountains.
All Scriptural dictionaries agree that the name "Ethiopia" is "Cush" in the Hebrew language. The name, also spelled as Kush, is derived from Cush the eldest son of Ham, who was a son of Noah. He was the brother of Canaan (land of Canaan), Mizraim (Egypt) and Phut (Libya), and the father of Nimrod, the first one called king. He reigned in Babylonia. (Genesis 10; 1 Chronicles 1))
To the Hebrew mind the name is next after the individual who originally bore it, for the descendants. The names in Hebrew language are essentially race-names and attached to the people rather than the place, and applicable whosoever the ethnic group may move, settle, migrate again and re-settle.
If an ethnic group split, and became two groups in different places, each could still bare the original name. The descendants of Cush may have split, one part remaining in Asia, the other migrating to Africa to become the Ethiopia we still know to  this day.
The name Cush have cropped up in many places. There is today a "Hindu Cush" in Afganistan and on the border of Pakistan by the Russia. With a name which appears to have moved about so much, it is better to locate "Cush," at the time when Genesis was written, by the river, rather than try to locate the river by the wandering name "Cush."
Cush is traditionally considered the ancestor of the people of the "land of Cush,"an ancient territory that is believed to have been located on either side or both sides of the Red Sea. As such, it is alternately identified in Scripture with the Kingdom of Cush, ancient Sudan, and/or the Arabian Peninsula.
The Book of Numbers 12:1 calls the wife of Moses "an Ethiopian woman," whereas Moses' wife named Zip'Porah is usually described as hailing from Midian. Ezekiel the Poet, a Jewish dramatist who wrote in Alexandria around the 3rd BC, has Zip'Porah describing herself as a stranger in Midian, and proceeds to describe the inhabitants of her ancestral lands in North Africa: "Stranger, this land is called Libya. It is inhabited by tribes of various peoples, Ethiopians, dark men. One man is the ruler of the land; he is both king and general. He rules the state, judges the people, and is priest. This man is my father and theirs."
Another person named Cush in the Hebrew Scripture is a Benjamite who is mentioned only in Psalm 7 and is believed to be a follower of Saul. The tribe of Benjamin is significant in biblical narratives as a source of various leaders including the first Israelite king, Saul, as well as earlier tribal leaders in the period of Judges. According to Genesis, Benjamin was the result of a painful birth in which Rachel his mother died, naming him Ben-Oni, "the son of my pain,"immediately before her death. Instead, Jacob, his father, preferred to call him Benjamin meaning "son of my right hand."