My great grandmother's maiden name was McCoy.
She was my father's paternal grandmother.
The male descendant of John C. McCoy took a Y-DNA test.
John C. McCoy was the descendant's great grandfather.
Thank you so much for your help. I've hit a brick wall with determining my great grandmother's parents. I have a great deal of circumstantial evidence which points to John C. McCoy being Etta's father, but nothing definite. I'm hoping that DNA testing will either confirm or refute their relationship.