Tammy--
I'm just now receiving my digest version of Westfalen-L, so others have probably already answered your question, but I'll add my 2 cents. I think the gentleman who suggested it might be "Platt Deutsch" is probably right. The term refers both to the language and people of the North German Plain, the coastal lowland about 80--100 miles wide bordering the North Sea. It is commonly translated as "Low German", referring to the lowlands where they live. It is seen spelled all sorts of different ways, including "Platte Deutsch", "Plautdietsch", "Plattdüütsche", Plaitte Deutsch", etc (some actually different but related dialects of Low German), so it's a very short hop to your "Plaug Dutch".
My ancestors came from Minden, on the Weser River at the south edge of the North German Plain. It's an interesting culture, kind of a mix of German and Dutch. If you are interested in any additional information, please ask.
Dan Steffen