User blog comment:FairyRaven/Fairy Tail Chapter 336: In Order to Live Today to the Fullest, Review and Commentary/@comment-180.194.29.221-20130621113353/@comment-7418318-20130621153626

Pain and Pein are just two different ways to "translate" the term (just like Charle, Charlu, Carla and Sharlu or Purehito and Precht), but they are still one and the same thing in the original.

And if that's not good enough for you, Pein is one of the possible german translations for the english Pain (along with Schmerz, Leid and some other, less used terms).