I am a HoltrOp
From what I know the name Holtrup/Holtrop had various spellings during the midevial times. I don't know anything about them being Danish but anything is possible.There were Holtrup's/Holtrop's in Germany in/around 1200.Burg Holtrop, a Castle once existed and my ancestors came from there.
Mine line eventually went to Netherlands in 1624.
Felix Unger....ya right.Right off a TV show, "Odd Couple" right?
Janet