Too posh to make sense

OK...it's' been bugging me all day and I'm too lazy to look it up.
I need to know: How many pounds are in a stone?

I keep hearing the british researcher down the hall exclaim about how her husband msut have put on a stone over the holidays. Like it's bad.
Now that word is bouncing about in my head (mostly as I have no idea what it means...*ahem*) and I must know...what stone? Was it once based on a stone? Was it a *shiny* stone? A valuable one at least?
Did it have teeth?
What?
Is it just a polite way of making a weight seem smaller than it is?
I imagine it's linked to what some King did once with a rock or weighed or threw at someone before he died...am I getting warmer?

At least try the METRIC people.
Come on. Kilos maybe?
A whiffin of a tonne?
Sheesh!




But, Seriously tho. Anyone?
I'm dead curious...