Kēlen
... In its concultural setting, Kēlen is spoken by an alien species (the Kēleñi) ... Kēlen is mentioned prominently by Sarah L Higley in her book Hildegard of Bingen's Unknown Language An edition, translation and discussion (Palgrave Macmillan 2007, The New Middle Ages ISBN 1-4039-7673-2, ISBN 978-1-4039-7673-4) where she discusses Lingua Ignota in the context of constructed languages up to the present day ...