Etymology ...Historically the word suggested poor, white rural Americans with little formal education. Historians point out the term originally referred to the strong Scots-Irish of the back country (as opposed to the English of the seacoast). Thus a sociologist reported in 1913: "As the plantations expanded these freed men (formerly bond servants) were pushed further and further back upon the more and more sterile soil. They became 'pinelanders', 'corn-crackers', or 'crackers'." 
Folk etymology There is also an apocryphal belief that the term dates back to slavery in the antebellum South. The popular folk etymology is based on slaver foremen using bullwhips to discipline African and African American slaves, and the sound of the whip being described as 'cracking the whip'. The foremen who cracked these whips are believed to have been known as 'crackers'. 
Examples of political usage "Cracker" has been used among African Americans like Malcolm X and Black Panther Party during the Civil rights movement and is considered an anti-white ethnic slur among African Americans.
In the 2006 movie All the King's Men, Jack Burden, played by Jude Law, refers to one of Willie Stark's opponents as a "cracker".
In 2008, Former President of the United States Bill Clinton used the term "cracker" on Larry King Live to describe white voters he was attempting to win over for Barack Obama: "You know, they think that because of who I am and where my politic[al] base has traditionally been, they may want me to go sort of hustle up what Lawton Chiles used to call the 'cracker vote' there." '
So Malcolm X used it, Bill Clinton used it, Jude Law used it, and yet some people are offended that I have used it. My use of the word "jarab" was not as protested by my American friends. Whatever dude. I apologize if you are offended, and I thank you for forcing me to learn the etymology of the word.