Well, I kinda didn't know it untill now recently when I talked to my brother. To make a long story short, the full name is Nerion Saiarion, and Nerion really means Marius in elvish, and Marius is my brother's name. He doesn't quite remember what Saiarion means, but he think it means "the Wise" or something like that.
One day (in the early days of World of Warcraft, I walked into his room and asked what he was doing. He said he was making a WoW character. Since he spoke elvish language, he decided to play as a night elf. He also decided to choose an elvish name. He wrote "Nerion" and then he stopped. "Tell me something about my personality," he asked me. "Well, you're very smart," I replyed. (Which is true since he've only gotten A, B and maybe B- on tests at school.) He found the word he was looking for, which became "Saiarion."
Actually, I have another forum user. But I thought the name was kinda unoriginal, so I asked if I could start using his WoW username myself. He said yes, and I created a new one.