Click on the hyperlink:
Peggy.
It came from
Margaret ->
Meg -> Meggy / Meggie ->
Peggy. No one knows why the M got turned to a P though.
You could use
Megan,
Magdalene /
Magdalena /
Magdalen,
Magnolia,
Magnhild, Magna (fem.
Magnus), or even
Omega as a full name for
Peggy. (Though personally I think
Omega's a bit of a stretch.)
Miranda