Earthdog
An Earthdog is a guy who knows every word to every Iron Maiden song, even the ones that don't make sense. They talk about Maiden like it's their ex and they still hate them.
At the Maiden concert, the guy next to me knew every lyric. He was an Earthdog. I was just there to sing along and not get yelled at.
My buddy went to a Maiden concert and came back with a new nickname. He's an Earthdog now.
My uncle turned into an Earthdog after he heard the new album. He hasn't shut up about it.