Skirt steak traditionally gives Tex-Mex fajitas their characteristic flavor and texture. This long, flavorful cut comes from the diaphragm area of the steer and is well suited to quick, high-heat cooking.
The word fajita comes from faja, meaning “strip” or “belt,” referring to the shape of the meat. In the United States, the dish became especially associated with restaurants serving sizzling strips of grilled beef with tortillas, onions, peppers, and condiments.
Modern restaurant fajitas may use chicken, shrimp, or other beef cuts, so the word now often describes a preparation rather than one exact ingredient. Historically, however, skirt steak is the defining traditional cut. Cutting it across the grain after grilling helps make the chewy muscle more tender.