I always liked the theory that Han was intentionally using nonsense jargon, to see if Obi Wan would pick up on it. To see how gullible he is. And Obi Wan just went with it cause he was kinda desperate to get off the planet, what with the stormtroopers snooping around looking for the droids.
I’ve seen forms of this joke quite a lot in the last few years, and it never fails to make me laugh.