I posted this on sa too but it's really a cruiser shortcut more than anything I think.
It's called the "bubble knot", in the knot tying book I had on my coffee table. For use with a one-part jib sheet. I was going to cut my sheet in half and put eye splices in the ends so I could use an amsteel soft shackle to hook up the jib, but this took me 5 minutes to tie and does almost exactly the same thing.
The loop goes through the clew, then the knot secures it.