The first part of the name is derived from Mei the goat in the soft-core furry porno Arashi no Yoru Ni. The second part is Youtube Poop jargon. It isn't necessarily the AIDS that blacks and gays get. In short, AIDS in YTP is overused memes like Mama Luigi and New Hydrating Volvic Revive.
He seems to have began making Youtube Poop in 2007 under the name "TheGizmaluke," but because of the copyright uncertainty about YTP, he had to make alts (Why does BrocksDubs and Jimmy Kimmel Live get paid for their shitty interpretation of YTP though??). He's probably most famous, however, for his taking credit for the Youtube thumbnail exploit of 2008, where Smosh, kidrauhl, and other video thumbnails were changed to the My Melody anime character Piano Chan or some Mongolian-looking guy among other things. After his popularity died down and 200 accounts later, he DMCA'd his own memorial channel and possibly some other things as well.
He sort of went "poof" around 2011. Some say he left Youtube, never to return again, some say he continues to poop (as in make YTP), hidden among us, but still some say he got a life (not likely since he's a yiffer) or was arrested by the FBI for looking at too much underage Hentai.
His history is somewhat unclear because a.) he's a troll, and b.) there's a crappe-tonne of impersonators.
Also, he invented sentence mixing but no one cares about that.