Andrew is correct. It is because of the distinctive lines.
"The long ribbed bonnet, hunkered-down roofline and sweeping rear pillars, leading to the distinctive boat tail and the massive, sculptured rear wings are all retained, as is the unique body side crossover line (which gives rise to the vehicle name). It starts as a concave, indented crease behind the front wheel arch and crosses over the car's flanks - 'crossing' to a convex crease mid-door - then sweeps back to highlight the edge of the rear wings and delineate the tail lamp clusters."
http://autoweb.drive.com.au/cms/A_55...wsarticle.html
If the name had anything to do with the joining of Chrysler and Benz, they would have had to call the vehicle either the "Misfire" or "Backfire", LOL.