Calendar with no events created in iCloud

I just noticed today that there was a calendar in the iOS calendar app that’s synced to iCloud that I didn’t create. It was just named a long string of numbers and characters with some dashes in between them. At first I thought maybe Zoom or some other third party app created it, but I don’t know if that’s even a permission that’s allowed. There’s no events, and I don’t remember ever receiving an invitation to join it like some other people experience with spam calendars. Has anyone else seen this?