These are a favorite around here.  Wikipedia tells me that fajita is the Spanish word for what we call skirt steak.  I’ve been dinged by pedants at another venue for calling these flat iron steak versions by that name but was defended by plenty of others who cited common usage.  Nowadays any grilled meat served on a tortilla can be called a fajita, chicken is a popular substitute.  I think you could as easily call these tacos but the grilled onions and peppers, along with the thinly sliced meat are the tell.