I can't find the name in any of my books. Ancestry.com says, it's of German origin:http://www.ancestry.com/learn/facts/Fact.aspx?nf=&nl=&fid=5&ln=Radenbaugh&fn=&o_xid=0040803744&o_lid=0040803744
But it doesn't give the meaning. It does have "BAUGH" though, German BACH, meaning "someone living by a stream". (The Dictionary of American Family Names, Oxford University Press)
Now to the RADEN part: "Rad" means "wheel" in German, so maybe there once was a mill by the stream. But this is just guessing.
Another idea (even wilder): The BAUGH part could be short for "bauer", "builder", and Radenbaugh would be someone building carriages. RADEMACHER ("wheelmaker") is a traditional occupational name for a cartwright. Menke, where are you?! I'm sure, he can dig up better information.
You may find this helpful, too:http://www.genealogytoday.com/surname/finder.mv?Surname=Radenbaugh