Apologies if these have been mentioned before: The MLB website calls the Colorado Rockies the “ROX”, and the CA/Anaheim/LA Angels “Halos”.
Come to think of it, apologies for having written ROX and Halos.
FWIW, “Halos” is a legitimate informal nickname, in the sense that I have heard games on the radio where the announcers call them that. I don’t know about “ROX” but they aren’t really on my radar. I grew up in Southern California, so the Angels were a local exercise in futility.