[Graham Boak]

Wild geese? There was considerable emigration from Catholic Ireland after the Protestant victory in the Battle of the Boyne. These became known as the wild geese: there are a number of folk songs on the theme.

Napolean had a general (Marshal?) with a Scottish name. Macdonald, I think. Presumably he left as part of the Stuart/Jacobean unpleasantnesses. Catholic again.

Not so sure about Pitcairn: surely Scottish but not necessarily part of the major emigrations.

De Lacy sounds pretty Norman to me, but with the O'Brien link that again suggests the wild geese.

Yes, further information would be interesting.