'Emo' was first used around the mid-1980s in Washington, DC, where American punk rock bands such as Rites of Spring and Embrace would become spontaneously emotional during what had previously been traditionally aggressive performances. Hence the emo tag (short for 'emotional') started to get used.
This scene grew in the '90s due largely to the breakthrough success of 'emo-core' heroes Fugazi, but by the new century, the term emo was being associated with more commercial punk-pop acts such as Jimmy Eat World, although none of these bands were willing to define themselves as emo.
I am SAD!
6 years ago