It is weird that Han would say that. It is even weirder because, unless I am missing something, they never even say Oh My God! Or even take his name in vain. But then you gotta think about. Greek Mythology did not have A God, it had several Gods and Godessess. But they did have a Hades. An after world. And that is exactly what Han Solo could have meant. But that is just my theory agreeing with more previous answers.
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One thing that bothers me about that though is that they took the time to come up with the Spice Mines of Kessel and that wasn't explain, though we all got that it was implicitly bad. Why not do the same with Hans words and let the audience figure it out?
I think the translation idea does work best though...