Mine was just the first thing that came up when I was registering my Aol account so I kept it and it is my username for pretty much everything ever since!
Surprisingly enough, when 12 (ish) year old me went to go an make a Steam account, the name Legend was taken. This was one of the alternate ones recommended, and it turns out that the numbers also have some significant meaning in my family (birthdays and such). My alt. account Ceogorach is just Cegorach from Warhammer 40 000 with two letters swapped around.
According to the Urban Dictionary, my name means: An amazing guy that can be a jerk but is extremely funny and sweet. He smells amazing and is average height. He may not be your first choice in a guy, but after you date him you'll want him forever. He listens to everything you say and he's protective if someone hurts you. you can trust him with anything and know he won't tell anyone because it's just who he is. He's a great football player and swimmer. He won't leave you for someone else, but you have to watch because that's his problem, if he finds someone else he may date them and you too. But that isn't common, he's a great guy and one of the best boyfriends a girl could have. He's cute too and the best kisser on the planet. And a girls dream guy after you get to know him. The 107 was just a random number.
My name originated from when I was like 10 and a cool xbox360 COD memer. Name was "oi Shockwavez v" or something. When I made my minecraft account like a year later I just used the same thing but changed it a bit to "oiShocKWavezv". I have since realised that name sucks and prefer to go by the closest thing to just "Shock" as possible for continuity's sake. I would do urban dictionary too but the result is about getting poop on your booper.
I once made a picture of a guy who shot nukes from his right index finger. Someone already had "epicpoke" on MC, so I added the underscore and 8.