The G-D reference is to Her Soldier (vol 6, 125-6). I don't have that one. Bruce Olson put the earliest date at about 1635. The other Peggy and the soldier is better known nowadays as Mary and her Gallant Soldier, I think; as you say, it's a completely different song.

"He bit her and he kicked her he called her horse"... I like that. What will they think of next!