I was watching the movie (the green land) and there was a dialogue in this movie that made me confused.
Before that, I had always heard that when you want s.b do s.th, you say (do this for God's sake). But in this movie, one actor said (God sakes) although we have (sake) only as noun but not as a verb.
I think it might well be an error that has become fairly common usage. For one thing, it's easy to say, especially with emphasis when angry. It's hard to make a logical analysis of the words. You'll also see it as one word.