His wikipedia page lists him as having quite a peculiar nickname. However it gives no detail on the source of it, or even having any contact with Americans! How did this World War I general famous for commanding troops on the Romanian and Serbian fronts end up being known for his actions towards America?
According to Inside the German Empire in the Third Year of the War by Herbert Bayard Swope it wasn't a personal nickname. It was a name applied to people who argued for unrestricted U-Boat campaign without concern for whether or not it would trigger war with United States and ah "talked a big game" about what they would do if the Americans ever showed up. This was premised on the notion that the US was completely unprepared ship sufficient troops across the Atlantic and would thus keep munitions at home instead of shipping it to England.