Haitian slaves were cruelly treated--many seeking to end their miserable existence. However, cruel to the end, their masters found a way to keep most from committing suicide. They declared that if they committed suicide, the miserable slaves would be enslaved eternally. They'd hang in an undead or zombie limbo unless they ate salt.
While slavery ended, Haiti continued having zombie trouble. I'll leave you to read about it. For me, it's an important reminder of a great truth: Jesus calls us to be salt--offering everyone the hope of eternal life that we have within us (Matthew 5:13).