Now that I think about it, our Southern “ants” can sound a lot like “ain’ts”, depending on how country the niece or nephew is. eg: “Ain’t Bea” from The Andy Griffith Show.
More of a shortened dipthong, part of the dialect in regions settled by Scotch-Irish. Not so much “ain’t” as “aiunt.” You hear it in other words too. “Home” becomes “haiume,” and so forth. It’s tough to spell it phonetically, but if you’ve heard it before, the spelling is about as close as you’d get without getting really technical, lol.