Where did pickled bologna originate from?

I don't have any evidence for this claim, but I'm pretty sure it's German. Pickled bologna is often referred to in the Midwest as "a Michigan thing". It's roots in Michigan culture come from Koegel's Meats - a meat company started by a German man who immigrated to the US and then to Flint, MI. Koegel's has been around for 100 years and they are responsible for pickled bologna madness that Michiganders have become known for.