The first Fox-based Mustang was seen in 1979. Fairmonts and Thunderbirds from the 80's, and a bunch of other Fords, were Fox-derived too. These model names probably don't mean much in Australia right? I've never heard of an explanation of why the name was chosen, but it was Ford's internal name for the platform, it doesn't appear on any car.
<P ID="edit"><FONT SIZE=-1>Edited by Ollie on 03/17/01 11:59 AM (server time).</FONT></P>
The Fairmont (and Merc Zephyr) came out as a 1978 model, Mustangs were still Mustang IIs. Fairmonts are the first Fox chassis Fords and all Fox Fords are based on the Fairmont platform. This included '80-'81 Granadas, '80-'82 Thunderbirds and Cougars (and to a lesser extent, '83-'88), the "baby LTD", and a Lincoln (can't remember name or year).
All I can remember is that Fox was the code name for the chassis's developement but don't know where it was derived from.