Skirt steak can be found in the plate primal. There are actually two skirt steaks, and although they look similar, they are different in several key ways.
The inside skirt is the transversus abdominus muscle and is named for its location inside the body cavity. The outside skirt is the diaphragm muscle and is full of flavor because it is constantly in motion.
The outside skirt is more desirable because it is more tender than the inside muscle. The outside skirt has a very pronounced, coarse grain that runs across the narrow portion of the cut. It is very important to cut this steak against the grain to maximize its tenderness.
The skirt steak was the original cut for fajitas. The word fajitas translates to “little skirts” or “little bands” and is derived from the way skirt steak looks. As fajitas, and skirt steak, grew in popularity restaurants started using other beef cuts for this popular dish