It comes from black people who noticed the white people having pale skin and relativly dry much like a salty cracker wafer.
It was first used and publicised by the Black Panthers and Malcome X who at the time said White Cracker. It was also used by Bill Clinton to describe white voters to win the vote of black people in the US.
White people think this word comes from Slavery when the white man would use the whip or cat & 9 tails, which is false and wrong.
The word originated in the Southern states in the US and in Britain.
The word can also be used to describe "Poor" white people on welfare from trailor parks used by the white man.
Conclusion: A derogatory word to describe the White man, like honkey and cracker baby. Though white people think its no offensive, it is very much so. That if you call them a cracker, there face will Turn red immidiatly.
black man: hey cracker
black man: Whats good cracker, you do know that every race other then crackers hate you.
white man: i though so, thats why I dont have friends..
black man: yeah, that might be part of the reason
No one is fuckin better than anyone they are equal, until your actions or reputation lowers your social status and respect, of course.