Back that A(ss/zz) Up

Does the phrase “back that ass up” possess enough expressive creativity to be copyrighted? We may never know, since the Fifth Circuit decided its appeal in Positive Black Talk v. Cash Money Records on a plain error review of the jury instructions on probative similarity and the relationship between access and similarity rather than on originality of the key phrase.
How Appealing: “This appeal arises out of a dispute concerning the popular rap song Back That Azz Up.”