This is the Wikipedia page for "Verteilungsgerechtigkeit", and this is the Google translation of that page.
There are various books out there that discuss Gustav Schmoller's ideas of Verteilungsgerechtigkeit, such as 1, 2. There are of course other intellectuals to be named besides Schmoller(Such as Adolph Wagner), but this long German word is your key to researching this if it suits your fancy. You will get results that are in the German language, but they can be translated on the fly online.
If these progressives want to import German ideas or rely upon them, fine. But they do not thereafter get to act as if they were the smartest people in the room and came up with something brand new out of thin air, and when they pass off crusty old German ideas as new American ones we should nail them on it. There really isn't anything new about progressivism at all, and in the end, tyranny is older than Liberty. Liberty is still the newest and the most unique idea in all the long history of man's relation to man.