🔼The name Cushan in the Bible
The name Cushan appears only one time in the Bible. The prophet Habakkuk reports that he saw the tens of Cushan distressed and the curtains of Midian trembling (Habakkuk 3:7). Since Midian is a country, scholars assume that Cushan is a country as well. Where that country might have been, no one knows, and most scholars assume that it's the same as Cush. But which one of the two countries named Cush could be also known as Cushan is entirely unknown.
🔼Etymology of the name Cushan
The name Cushan is the name Cush postfixed with the letter ן (nun), which might be a remnant of the familiar ון extension, which personifies or localizes the action of the root. Unfortunately, knowledge of the origin of the name Cush is irretrievably lost. The translators who produced the Septuagint translated the name Cush with Having A Dark Face, and that's what people have copied over the centuries. But Cush probably didn't mean that to a Hebrew audience.
See for a more complete discussion of the Cush conundrum, our article on the meaning of the name Cush.
For a meaning of the name Cushan, NOBSE Study Bible Name List reads the traditional Blackness and adds: probably the same as Cush. Jones' Dictionary of Old Testament Proper Names doesn't treat Cushan separately and lists it as an alternative spelling of the name Cush, which Jones translates with A Black Countenance. BDB Theological Dictionary does not interpret this name.