In the beginning (1967-68) Jaak, they were called "tilting body mounts" because nobody was using pans back then except the scale builders.
As magnets got stronger and motors more powerful, a new trend emerged of going full pan to really lower the center of gravity. First it was full pans attached to a brass rod or tube frame and then later just pans attached to key locations.
Eventually those pans became working parts of the chassis... droparm and side tilting pans.
The term "batpan" refers to the wings of a bat moving up and down so it is an easy association.
I have no idea who coined it.