A term originated in the sixties when the Blacks within American population felt that Whites where trying to completely wipe them out. It was calculated (perhaps correctly, perhaps incorrectly, i don't know) that America had 10 white people for every black person. It would then be a war without a winner if every black person killed 10 white people before he was killed. This was especially popular in the time of Malcolm X who was a militant leader, but strictly as a form of self defense. This phrase died out as Martin Luther King became a popular black leader, due to his non-violence preaching. I've heard that this phrase has cropped it's head up again in rap songs, which is not surprising due to the violent nature of the majority of rap songs and urban youth these days.