Yes, he had a nickname before, so he had to be named mightyena so if you evolve him that`s his name; if he had been named poochyena after having a name, he would have kept the name poochyena when he evolved.
I didn't ever really make any formulas; I just thought of the idea and pitched it to the community. I think someone who posted in there had a really good grasp of the concept, though. (I still think its a good idea but I don't ever seeing it succeed.)