My follow-up guess is that
Emerentius was taken to South
Africa by our
Dutch settlers, also as a feminine name but with spelling variants. The best known of these is Emmarentia, probably originating because
Emma is a familiar female name. I know a woman, now in her 70s, whose given name is Rentia (pronounced RENsha), a shortened form of Emmarentia.
I have not seen any examples of
Emerens or
Emerentius in local sources, but nor have I looked: census and BMD notices are not made public here, as a matter of policy, though this might be changing. Public records are kept in very few places and are hard to access and, one suspects, incomplete.