I have heard many different tales and stories of who invented the scream in music. From the likes of people saying the Led Zeppelin, Motörhead and Ozzy Osbourne era of metal were the ones to introduce it, to people saying it was invented in new-wave metal and post-hardcore, such as Bullet for my Valentine, Trivium, Disturbed and so on...
What I want to know is in the history books of metal and any other genres, when was screaming introduced?
Is it specific to one artist who created it?
If so, which artist was this?
Also comments on how and why it was introduced and used would be helpful.