Souse is a form of head cheese. Here in the south it is more similar to head cheese than up around the Cincinnati area. Made from the ears, tongues, and other head parts, just cut up finer than what you'd typically see in head cheese. Seasoned a little different, more pepper than head cheese. But in the Cincinnati area it has vinegar in it, making it more of a pickled meat.
I have people tell me they would never eat either one, I point out that many hot dogs are made from the same cuts of meat, just ground up into a puree, seasoned differently and stuffed into pigs intestines. Looks to kill........LOL