This is the 12611th most frequent German word.
welldorf
It seems "welldorf" is not a standard German word. It may be a misspelling or a proper noun (e.g., a place name).
In this sentence, 'Welldorf' is a proper noun used to refer to a place name.
Welldorf ist ein ruhiges Dorf in der Nähe von Köln.
Welldorf is a quiet village near Cologne.
Here, 'Welldorf' is referenced in a conversational context as a topic of discussion.
Ich habe gestern von Welldorf gehört, während ich mit einem Freund sprach.
I heard about Welldorf yesterday while talking with a friend.
In this context, 'Welldorf' is used as the destination for visits and admiration.