It's a matter of conjecture that 277 is based on 'Wife wrapped in Morrel's Skin' As far as I know even the earliest versions have no text in common. It is even possible that 277 predates Morrel Skin. However the 2 tales are so similar as to say they both contain the same motif, regardless of different animal and some of the methods employed. I think most people would agree that either one influenced the other or that they both derive from an even earlier tale.

Slattern Wife is a completely separate piece that has been crossed with 277 at some later date, probably no earlier than the 18thc and likely not until the 19thc.