@Boberholzer I refer to it as the “Rebel” flag because the Confederate States of America aka The Confederacy never officially adopted it as their national flag. However, near the end of the war, it was incorporated into an official design. While it was originally a battle flag for The Confederacy. Over time, the flag has become widely known as the 'Rebel' flag and has been referenced in pop culture in that way. A quick Google search for 'Rebel flag' overwhelmingly returns results featuring this flag. If you want more information on it there's a Wikipedia article that explains it more.
