Hi Roxana,
There wasn't a sudden explosion of "Arthur" like names - there are four from, I think, the mid 6th through 7th centuries (I'm working without references so my details might be wrong). I also recall that these occurrences all either appear in Irish, South Welsh or in Dalriadan Scot lineages - in other words the earliest occurrences are all linked with IRISH settlers in Britain or with Ireland itself.
This is, in itself, interesting as the closest mythological figure we have to Arthur is Fionn - one wonders about a local name for the figure...
Also interesting is that, where we have evidence that the Kings of Powys included Vortigern in their lineage (see the Pillar of Eliseg), the Welsh and Strathclyde genealogies are largely silent about being descended from Arthur. Of course, the same is true of Ambrosius Aurelianus! Even if Arthur had no children it would be strange that such an important figure wasn't co-opted in at some point.
Unless we count the one line from Y Gododdin ("He was no Arthur") which MAY have been a later insertion we have almost nothing from British sources about the name Arthur until Nennius.
All of which goes to show that the Dark Ages wasn't such a bad name after all
Pete
God is our guide! from field, from wave, From plough, from anvil, and from loom; We come, our country's rights to save, And speak a tyrant faction's doom: We raise the watch-word liberty; We will, we will,we will be free!