Checking back on Sweet...sele = hall, sele-dream = festivity ;)
seld = hall or seat. So that is where Atkinson is getting his info from.
Bonney article. in WAM 61 Pagan saxon boundaries and burials in Wiltshire; quoted in Josh Pollard's Avebury.
Pollard also gives Waden's Hill pagan name as weoh-dun meaning idol, holy place or shrine (earliest ref for name 1639). Interesting, push back to R..... times and there seems to be three wells around Silbury that could have been sacred, the R.... settlement on Waden Hill being a tourist place for this sacred area perhaps/ or posting station for horses between Verlucio and Cunetio. Considering the saxon poem The Ruins, it could well be speculated that Silbury held its special powers thro both these periods.....