This word came from a misunderstanding between my Wife and Myself. One day while putting the groceries away, I asked her where the milk was. She replied "it's in the bag"! There were at least 10 bags and I said "Which Bag"? She came around the corner and said "What did you call me"? I said "nothing, I asked "which bag""! We both laughed because she thought I had called her a "Bitch-Bag".