The identification of Osla Gyllellfawr with Ossa, grandfather of Ida, king of Bernicia, as suggested by corrupted late entries in the Bonedd y Saint, shown below, is incorrect:
|Gen.||ByS 70||ByS 71||JC20 17 seg.
|3||Osswallt||Oswydd aelwyn||Gwynbei drahavvc||Ceit|
|2||Mwc Mawr Drevydd||Douc|
|1||Ydolorec vrenin||Offa kyllellvawr||Llewarch hen|
The names given in the above chart are in the manuscript form. The first two individuals in ByS 70 are Oswald and his brother Oswiu, wrongly shown as his father but corrected in the above table. The third name would then be their grandfather, the Bernician Æthelric, wrongly shown as Oswiu’s father and this has also been corrected for. An alternative interpretation, which would be correct in terms of parentage, would be Oswine son of Osric son of the Deiran Æthelric.
Bartrum maintained the first name in ByS 71, Eda Glinfawr, is Æthelric’s father, Ida. However, that is impossible since Eda can safely be placed in gen. 4, more than a century after Ida. This conclusion is arrived at by noting Eda was the grandson of Mwng Mawr Drefydd who was in conflict with Mechydd ap Llywarch Hen. Llywarch can safely be placed in gen. 1. Furthermore, as Ossa was Ida’s grandfather he would have been far too early to be a contemporary of Arthur.
It would seem that the author of ByS 71 added cognomens that did not actually apply to Eda and Offa but instead belonged to other individuals with similar names. So, Glinfawr came from the name of the father of Ecgbert of York, Eata glinmawr, mentioned in HB 61. Likewise, Offa’s cognomen derived from that of Esla, see Dating the Wessex generations.
Melville Richards’ identification of the 8th C Offa of Mercia is unlikely for the chronological reason. Also, the dissimilarity in the names suggests it is doubtful that Osla was the Kentish Ochta as suggested by Idris Llewelyn Foster.