“whirring wings.” Several interpretations have been set forth as to what “whirring wings” refers to. Ethiopia was known by some for its large amount of insects, so that has been set forth as a meaning. Also, the route of the Hebrew word means “shadow,” and Ethiopia was close enough to the equator to have the phenomenon of sometimes having a shadow fall from the north and sometimes from the south, and so “shadow” has been set forth as a possible meaning, and the TNK version has “land in the deep shadow of wings.” However, it seems more likely that the correct meaning is the one found in the Septuagint and Aramaic Targum, which say the phrase refers to ships that race up and down the rivers, and would have had the “wings” (sails) in the wind. Also, that interpretation fits with the use of rivers in the second stanza and in Isaiah 18:2, which speaks of sending “swift messengers” by sea.
“beyond the rivers of Cush.” Cush is the biblical country that was south of Lower Egypt and encompassed much of what is now Ethiopia, and because of that some versions have “Ethiopia,” but Cush and Ethiopia do not have exactly the same boundaries. Biblically, “beyond the rivers of Cush” was considered the end of the earth, so the phrase “beyond the rivers of Cush” meant “to the ends of the earth.”