Jim Shooter has posted the first part of what he called "The Secret Origin of the TRANSFORMERS – Part 1". At the time, circa 1984, he was Editor-in-Chief of Marvel when Hasbro brought the franchise to them to help create the names and stories that would be used to market the toy line. It was the same model that they used in relaunching G.I. Joe where Larry Hama was given a chance to name, create the history and bios for those characters.
Any case in part 1 he discusses how the project came to Marvel and some of the early bumps that occurred in developing it. Of note is the mention of Dennis O’Neil who is credited with coming up with the name of Optimus Prime. The 1st part of the story (with more to come) can be found here.