"ARGO" was the name given to the script that was chosen by the CIA op. (Mendez?) and the Hollywood guys back during the planning stage. The original movie story line was something about a sci-fi journey to unusual, exotic & desolate places. So, they figured Iran was exotic and had desolate film locations and away they went. One of the Hollywood guys came up with "Argo".
Jason & the Argonauts? -> His ship was the Argo.

Here's an interview with the CIA guy.
The True Story Behind Operation

Kerry, I agree that the cars chasing the 747 at the end was kind of hokey. I wonder just how close the escape actually came to ending in failure?