Obviously it comes from the French and German for Yes, based on the fact that the primitive version had two markers, Yes or No. The pointer, usually an upturned glass, would be directed to one or the other by sleight of hand by the manipulator.
We used to have a laugh doing that when I was younger. My friend used to live in a big spooky old house in North London and it was our party trick when we came home p1ssed from the pub. It never spelled out anything that made sense but the glass did move and I don`t think anyone was pushing it. We all took turns sitting out but the glass still moved. I think maybe it`s just energy/warmth from people`s fingers that makes it move.
Ohhh, now I'm excited! No doubt we will all be a bit... er.. tipsy, but I reckon it should be a bit of a laugh!
I will absolutely DIE if anything actually happens! :D