Grestien's Yder has in common with the Yder of the Brut these features:  he is the son of Nut and is an Arthurian knight.  Further than this he cannot be connected with the legendary, historical or the romantic Yder.
    In romance, Yder's achievements are the fight with the bear and the fight with the giants, and his love of Guinevere.  The first record we have of the giant incident is that by William of Malmesbury (1060?-1143).  Here, Yder disappears after the combat and Arthur thinking him dead, has mass sung for him at Gastonbury.
    In the Mabinogi of Geraint and Enide Yder (Edern) performs the same part as in Erec, but in the older tales he is presented more favorably.  Kulhwch and Olwen mentions him as an Arthurian knight (Mab. I, 203).  In the Dream of Rhonabwy he commands an army of men of Denmark (I. 300).  Here he is also one of Arthur's counsellors.  Therefore, Crestien's treatment of Yder seems to be for the most part independent.  There seems to be no precedent for connecting him with the Sparrow-hawk adventure, but the association of Yder with the court of Arthur may have developed from Wace. (The Influence of Wace on the Arthurian Romances of Crestian de Troies, Hopkins, 1918)