As many Warlocks and other practitioners of the dark arts already know, our minions summoned from the Twisting Nether are essentially disposable tools however in any case if you find yourself wanting a more powerful name for your minion then it is quite easy to do.
Simply make a macro and enter the following script
/script PetAbandon();
Summon the pet that you want a new name with, then run the macro. It should despawn the pet and upon re-summoning your pet will have a new name. Keep in mind however that each name will be randomized due to the chaotic energies of the Twisting Nether but eventually you should settle upon one of your liking.