Some insight into the real history of this song: "Buttermilk" (and "Portland", in at least one version) are almost certainly a corruption (in my opinion) of Portumna in Galway, Ireland, site of the Wild Geese Heritage Museum*. Portumna Castle is surely on a hill, and the Wild Geese were Irish soldiers serving in various European countries in the 16th, 17th and 18th centuries, especially those who went to France in 1691. (*Flight of the Wild Geese, Wikipedia)