Get it? Han "Seoul-Oh"? Han Solo? I'll give you a moment whilst you collect yourself together - all that uncontrollable laughter really must've taken it out of you. Done? Okay.
So, yeah, because this character is called Han and is of Asian descent, it made super-natural sense that the Fast and Furious writers would give him a surname that plays homage to the iconic character of Han Solo from Star Wars, as played by Harrison Ford.
Anyway, this character started out being known as Han Lue, back at a time when somebody hadn't made the obvious and undeniable connection between the words "Solo" and "Seoul" (capital of South Korea, if you're wondering), and then we were gifted with this little easter egg-ish moment where we were given the chance to glimpse Han's surname on one of Fast Five's many computer screens.
Great, huh? Now don't get cocky.