*Outigirn is a name that appears in HG 10. But in JC 5 his name has been corrupted to *Kyndeern weldic.
A later individual with the same name is to be found in HB 62:
Then Dutgirn at that time fought bravely against the nation of the Angles. At that time, Talhaiarn Cataguen was famed for poetry, and Neirin, and Taliesin and Bluchbard, and Cian, who is called Guenith Guaut, were all famous at the same time in British poetry.
The document indicates that *Dutgirn or *Outigirn (Eudeyrn) lived in the time of Ida and Maelgwn. The corruption of the name Eudeyrn to Cyndeyrn that occurred in JC 5 may have occurred in the opposite direction, i.e. Cyndeyrn to Eudeyrn in the HB. Chronology suggests the HB reference is to Cyndeyrn Fendigaid ab Owain ap Cyngar who appears in ABT 18a and JC 13. He was not Cyndeyrn Garthwys ab Owain ab Urien Rheged of ByS 14.