Story highlights Trayvon Martin's friend said he described George Zimmerman as a "creepy-ass cracker"

The term injected race into Zimmerman's second-degree murder trial

"Cracker" has a murky history but generally describes poor whites

The slur is widely considered an insult among white southerners

With a single phrase, Rachel Jeantel , that friend of Trayvon Martin's, may have lit a fuse in the trial of his accused killer.

Asked by the defense what Martin told her on the phone that night when he first spotted George Zimmerman, she testified a "creepy-ass cracker" was following him. There is nothing illegal about that. Jeantel said she didn't even know it was a racial slur, and numerous commentators have noted that some in Florida use the term in a non-derogatory, colloquial sense.

But for plenty of rural, white southerners, "cracker" is a demeaning, bigoted term, and its appearance does nothing to help the prosecutors.

The origin of cracker is murky. Some sources suggest it came from overseers who commanded slaves. Others say it derives from a Scottish word for boasting. At The Center for the Study of the American South at the University of North Carolina , Bill Ferris says it emerged in the 1700s as a descriptive term for drovers who used small whips to move their livestock through the pine barrens along the Gulf of Mexico. "They were basically poor people. White people. A class of people who were landless."

Initially, cracker was not a pejorative term, but Ferris says it has become one, the equivalent of redneck. Its meaning and intensity as an insult depends on who is saying it and who is listening. For example, a white who might not object to being called a cracker by another white might consider Martin's use of the phrase offensive and evidence of ill intent.

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In the circumstances described in court, Ferris notes, it was more likely a quick way for Martin to say he was in danger. "If it is used by blacks (among themselves), it is usually with one meaning: Watch out. He didn't say it to Zimmerman. He said it to convey a message to a friend. He said, 'trouble is coming.'"

Still, even if Martin knew precisely what the term meant and said it with all the venom he could muster, does that matter?

Maybe. Under Florida's hate crime laws, Martin's words could potentially have been used against him had he survived the encounter and Zimmerman had taken the worst of it. That may seem far-fetched, but a state handbook advises that a hate crime may have occurred "if the commission of (a) felony or misdemeanor evidences prejudice based on the race, color, ancestry, ethnicity..."

Complicating the matter further: Despite suspicions among many case watchers that Zimmerman followed Martin largely because he was African-American, the only mention of race from the defendant in his call to the police that night about a "suspicious guy" came when he was questioned. "This guy," the dispatcher asks, "is he white, black, or Hispanic?" Zimmerman responds, "He looks black."

All of this may seem pointless to people who focus on the central fact of this case: No matter how the conflict began, police say it ended with an armed man killing an unarmed one. The debate over cracker may furthermore seem arcane to people who live north of the Mason-Dixon line, where cracker is seldom heard, and even when it makes an appearance, it is not freighted with decades of history. To be sure, cracker is not on par with the n-word, but it is nonetheless a sharp racial insult that resonates with white southerners even if white northerners don't get it.

That said, ask Ferris what impact the word will ultimately have on public opinions of this trial, and he is succinct. "I would say none." Views of justice, he says, are inextricably linked to racial attitudes. Many blacks will see this trial one way, many whites another way, just as they did in the case of O.J. Simpson.

But the broader public does not matter. What matters is the jury. And it is hard to imagine how it can help the prosecution for those six southern women to know Martin spent some of his final moments uttering a racial insult, no matter what he intended.