Well, I came up with InnocentBoy back when I made my Minecraft account. I didn't like the original alias I used, so I decided to come up with something nice.
I couldn't really think of anything, but for whatever reason, I thought I was innocent enough to have a username that pointed it out. So, InnocentBoy (no space or underscore, by the way) came to be.
Over time, I've admittedly sort of changed it up to be able to use it differently. So Inno became my alternate name when InnocentBoy is too long.
EDIT: So your name is just Alice + Cirno, Alicirno? Something tells me we should be friends, but that's probably a bad idea on my part.