"atoms_gf" wrote:in the latest Harry potter movie (and last) at the end Harry named his kid after Severis XD
First it is Severus, second in this particular case someone else had this name before

In France you can't give anything as a first name, it must "exist" in some way. I can't remember the exact instance, but some parents had named their child with initials. They were asked to find another name, and they settled for a name which existed while having almost the same pronunciation as the previously chosen initials.