I realise this is an old thread but I just joined and see nobody answered it.
The Rover Coupe was given the name Tomcat when it was a project car. It was the development name so the press and rival companies didn't know they were producing a coupe version of the 200. The name never actually made it officially to production but some people like to refer to their coupe as a tomcat. The Race series in the UK was sponsored by Rover but after some time Rover stopped backing it and they stipulated that the race series could continue but they could not use the Rover name. Therefore, the Tomcat name was adopted as a logical step forwards.
Hope this explains it enough