Because at the beginning, they were not popular. Generally, new couples didn't have a group name at all, so they just called it casually ... Once, they had a rare opportunity to go on stage, but they didn't expect to call it SOS first aid, but it felt strange, so they added an A in front of them, so they became ASOS, and they kept calling it down ... Xiyuan was a sister, so she was called Big S, Xidi was a sister, so it was called Small S as a nickname. ...