So rejected names:
Ahdin, Aicksar, Alfred's daughter, Amnell, Annatar, Appelsiinikki, Azazel, Buddha, Caladrius, Eklander, Ellé, Ephimachius, Felín, Filipecki, Haades, Jezebel, johannes, Juhoha, Julma-Hurtta, Kaaos, Kallen-Kallela, Klapi, Koivuniitty, Kukurtaja, Lord, Lucifer, Maï, Mielivalta, Nat8hquhs, Nex, Otawa, Paperi, Pelekkä, Punpuli, Puukko Armo, Raivomieli, Rikia, Rody's son, Rosmo, samsam, Saturnius, Sheikki, Sorína, Suudelmitar, Taawi, Tanyá, Tsygä, Tuoni, Uakke, Uhka, Ukonvaaja, Wiiru, Åriz
Some of them are easy to see why they were rejected. Like not starting with a capital letter, having a number in the middle. Others seem to be either because they have an association with a negative religious figute (Lucifer, Jezebel) or because it's offensive to a religious group (such as naming your child Buddha, which buddhists would have issue with). Also a title can't be name such as Lord or Sheikki. And why would anyone want to name a child Paperi (meaning paper). I don't see why Tuoni was rejected though, a name from Finnish mythology. One of the many Gods of Pain and Suffering, because Finnish mythology is all about pain and suffering.
Accepted names:
Aamuntähti, Aarnik, Anoo, Arsitar, Avreno, Bobandy, Ellandar, Feeni, Heito, Häkä, Juhania, Kide-Pilvi, Kimara, Konon, Korppi, Lapitar, Lourences, Messis, Mieli, Niittu, Petäjä, Piamon, Pihlajanmarjukka, Pihlamo, Poolo, Pöly, Sanervatar, Saturnus, Sjöbjörn, Taide, Torspo, Unikonsiemen, Wâânutamwee, Yennefer
Aamutähti is amusing (means Morningstar), because Lucifer was rejected, and means the same thing. Some Witcher fan apparently decided to name their daughter Yennefer. Names from fiction are usually accepted as long as they aren't some extremely negative figure.