Among the many traditions known to Southerners, putting peanuts in the soda is actually among the more common traditions like comfort food and sweet tea.
According to an article on the Coca-Cola website, the practice of putting peanuts in Coke goes back generations and extends from Texas to around the Carolinas.
According to Wide Open Eats, the snack was popular among blue-collar workers who didn't have immediate access to a place to wash up, so in an effort to keep their snack from getting dirty, they poured them into their Coke.
There is also another theory that is was an easy way to free up a hand in order to smoke and snack at the same time.
There is no way to know for sure how it really started, but one thing is for sure — it is a Southern tradition that continues to live on.