Mine is somewhat simple. As a Jr. High student, I foolishly thought I could make it in the world of webcomics. So, like 1000s of kids with Photoshop, I tried my hand at it, starting small with a Sprite comic I hoped to one day draw into an actual pen and paper comic. The comic was called "Rin of the Demon eye". Yes, it was BURSTING with originality.
I realized that I should probably make my forum and other site names comic-related so that if I wanted to actually get anywhere, I could use it as mini-promotion (Like, in my sig and stuff) But as "Rin of the Demon Eye" was a little too unwieldy as a username, I shortened it to "Demon Rin". But, pretty soon, I realized nobody was reading my comic, and it was flat out not very original. So I shelved it after like 20 issues, but the name stuck because so many people/places knew me by it.
Pretty sure this all went down long before I joined AP tho, because I'd found my niche on the internet as the Hellsing girl by being a co-admin at Bloodknight (which later kinda became my current site, Call To Arms) and was officially a scanlator by then.
But yeah, that's where it came from.