It's how we speak english in my part of scotland. It basically means that I have eaten so much that I couldn't possibly put another morsel in my mouth.
If I really went off on one you wouldn't have a scooby what I was talking about. I haven't actually spoken like that for a while because only peeps from a certain area of the country get it! When my grandsons come to visit it takes us quite a while to "tune in" if you like. They don't just use slang but they also speak so quickly it is quite unintelligible. But yeah it's cool to try and write. It's not something I think about at all. If you've read Irvine Welsh you will totally get it!
