OK, so.. why 'Ring'?
Is it because the phone rings? Or because if you were to look down the well it would be a circle aka a 'ring'?
OK, so I just googled it and apparently its because the girl would have seen a ring of light as she looked up the well as it was being sealed, but that sounds like an explanation that may be from the US remake (which I haven't seen) as there was certainly nothing like that hinted at in this film.
Formerly AD655321 I'm just a bloody normal bloke, a normal bloke who likes a bit of torture.