You may be thinking of the movie "Uncommon Valor" and I think it was a line delivered by Tex Randall Cobb, though I can't remember the exact dialog or his name for certain. I do remember that he was a boxer who tried his hand at film work.

I grew up with that expression and it was old in the south and in Texas when Christ was a corporal. There was another B movie of the late 60's - early 70's in which a villainous and corrupt policeman told the heroes, "Boys, you just bought yourself a bad case of old fashioned Texas whoop ass."

The good guys then proceeded to mop the floor with the crooked cops. When it was all over, the main hero leaned over the barely conscious cop and said, "We're from Tennessee and our folks invented old fashioned southern whoop ass with some cousins from Alabama and Mississippi when we had a chance to practice on Yankees and crooked lawmen."

Ask Honey or any of the other southern folks around here. We've been calling it that a long time, probably dating back to the invention of corn in liquid form. I remember a deputy in South Carolina asking a visiting trouble-maker from Michigan in a rural convenience store and watering hole just how long he'd been shopping for whup ass 'cause he'd just found a bargain. Then he and another badge totin' good old boy proceeded to deliver as promised.

I had not even started to school when that happened but I learned quickly that no wise person goes shopping for southern or northern whoop ass or whup ass of any kind. You see, I also heard it from several guys I knew when I was in New York City and from some others I knew in Florida in the early 60's. I think it was also used in a book by Erskine Caldwell or Tennessee Williams long before "Uncomomon Valor" was ever written.