There are many persons with the surname "weidung" many time before thomas was birth
There is a website called "Family search". On it you can see many documents of persons that already died. You can search specific documents using filters of location, birth date, name and surname. I searched "weidung" and i found many persons with that surname that lived many time before thomas was birth. There are at least 95 persons in Germany with this surname.
https://www.familysearch.org/en/search/discovery/results/?tab=preview&q.surname=weidung
I found what you are saying. So the name Weidung isn't fabricated after WW2.
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We also said in the article that the surname "Weidung" is a very localized surname which is only prevalent in the small town of Koblenz. It's also a fact that this surname doesn't figure in any of the records of German surnames history.
https://nvk.genealogy.net/map/1890:weidung
This is an example from 1890. This surname inexistent all over Germany. You can try any surname you want here.
You can easily fabricate such localized surnames, trust me.
There are surnames localized solely for the region, this is true.
But never for one town. In this case we have to do with a single, isolated family that most likely completely had changed their identities.
Even 'Balling' has more popularity.