Meredy
It had come from something that Meredy once heard Ultear say, something about being able to convey one's exact feelings to another. It hadn't made much sense to her back then, but then again, she was just a child so not much else had made sense either.
She had asked the others what she had meant, and was told that Ultear had meant that for the only way for people to understand one another would be to have them know the exact emotions of others, which was impossible, most of the guild had chuckled off. But Hades had said that it wasn't impossible, and that there was a type of Lost Magic that allowed you to do exactly that called Maguilty Sense.
This had interested Meredy greatly and she had asked if she could learn this type of magic. Hades approved and pretty soon, she was being instructed how to use magic that targeted one's sense of touch.
When Meredy learned that Ultear intended to travel back in time to prevent her horrible past, she realized that she would never get saved by Ultear either. It was then that Meredy decided that if she couldn't be saved by Ultear, she would make sure that she would never forget about her. When they reached the Ultimate World of Magic, Meredy would cast a spell of connection on Ultear so powerful that no matter how hard she tried, Ultear would never be able to forget about Meredy, and when her home was destroyed again, Ultear would come find and save her all over again.
Sorry that this one's so short, but I didn't really have much to go on with Meredy's past having been explained in more detail than the rest of the Seven Kin.