Yeah you're not supposed to give it names that belong to the other gender, can't have too many names, can't be a name that is used as a last name usually, and needs to have Finnish spelling and pronunciation unless one of the parents is foreign. So I dunno, maybe Gayer would be approved.
That said it seems they don't always apply the rules. There's one man with the same name as me, there's a few female Jesus's and Muhammeds and prolly other ones that don't fit with the gender rules