OSM documents the names that are presently used, not the names that are historically correct. With many other things it is easy, you just look at the signs, sadly water bodies tend not to have signs. DWG is not taking a position on what the "correct" name is for this body of water, we just ask that any change in naming is a result of community consultation and not a result of looking at archives. So the right way to go about changing the name of this water body is opening a discussion on community.openstreetmap.org, presenting your reasoning there and inviting others to comment. Then if a consensus is found, the name can be changed with a pointer to that discussion. Any name change that does not point to a community discussion supporting that change, will be reverted.