Originally Posted by Shadowlord X
He could be portrayed as a shrewd businessman who was nicknamed the Mandarin because of his tendency to dress in traditional Chinese garb at certain functions.
He doesn't even have to go that far. He could just be a staunch traditionalist in regards to decorum and manners and be given that as a derisive nickname, like why Harvey Dent was called Two-Face even before the accident in TDK.
Thinking further on it, the Iron Man movies have purposely underplayed the costumed monikers anyway.
The press named Iron Man. Stane told Tony they were 'Iron Mongers'. Tony asked Rhodey if he wanted to 'be the war machine'. I don't think Vanko is ever explicitly called 'Whiplash', though I could be wrong on that.
So the Mandarin moniker doesn't even have to be emphasized or even used, really. If he's Asian, and the leader of the 10 Rings, we know who he is even if they don't say it.