I first encountered the German "Black" family in Augusta Co. VA in 1700 court records when I was researching a Scotch-Irish family of Blacks that I believe to be in my ancestry.I saw several records for a Cutlip Black and was trying to find his tie in to the Scotch Irish group. I wondered if Cutlip could have been a nick name because of a harelip.But then I ran into the will recorded in the name of Cutlip Black.The will was in German and the testator was Gottlieb Schwartz (Cutlip Black).So here we had a situation in which the Englsh speaking community was using a rough trnaslation of his name (an actual translation would have been Godlove Black) while he was still known as Gottlieb Black in the German community.
I don't think he changed his name - the majority community and courts did it for him.
It is my not very scientific conclusion that the German Blacks in VA in early generations could be distinguished from the Scotch-Irish Blacks by first names.The Germans used Christian, Jacob, Henry, Joseph, etc.The Scotch-Irish used James, William, Alexander. etc.Both used John extensively.Of course, this may not have always been true and was less true as time passed.
I have always assumed my Blacks were Scotch-Irish but I leave a little room open in the possibility that they may have been German.