Except that Mason-Dixon is the border between PA and MD. And MD waffled about which side to join (as did a couple of other states, which actually DO lay south of Mason Dixon).

I'm not disputing word origins here, but "boundaries" were a highly complicated issue, even for a long time after the war.

And some one tell me why I'm remembering Yosemite Sam in a Confederate War Uniform chasing Bugs Bunny around now?

And grumble, I apologize, I was just trying to make a bit of an in-joke for people who remembered that sit-com from about 20 years ago in North America.
Which was also immortalized in the "Boot to the Head" sketch Dr. Demento has included on a couple of his CDs (yes Steph, I know they were Canadian too).

"The best defense is a good offense. You know who said that? Mel, the cook on Alice."