It's both geographical and etymological (and it's still a bit early for me too ;-)

'Silbaby' is referred to by Stukeley as Weedon Hill - I don't know if he's confusing it with Waden Hill, but the name Weedon Hill occurs elsewhere (in Bucks and Northants for example) where it certainly means a 'hill with a heathen temple'.

Pete, does Stukeley ever actually use the name Waden Hill? Stukeley seems to confuse Waden Hill with Windmill Hill sometimes. And what does he mean when he says (above link, last line), "This hill too is call'd Weedon-hill..." What 'too' is he referring to?