of course it's short for emotional, where do you think the term came from?
the beatles were emo. the deftones were emo. all the 80's michael bolton, brian adams, light fm people were emo.
i realize it's a specific style of music these days. but it's really not. that's the point of this thread i think. besides acoustic stuff like dashboard, the spill canvas, onelinedrawing, etc....the true 'emo' banRAB. every other band has emo in them. thats why metalcore turned into 'screamo'. & most poppunk is being called emo too now.