In another comment, one one of the other commercial services censored a prompt that contained “cox”, probably because it’s used as shorthand for “cocks” sometimes. Damned if I know what “Sibbo” would be tripping, though. Maybe “Sib” == “sibling” and an attempt to censor incest pornography, though that seems like a long shot. I don’t see any other component that I can possibly shoehorn into an objectionable sense.

Maybe it’s something in a non-English language.