Thanks for tip about Long Black Veil - I didn't know that!
And I'll look for that Sing Out magazine article, too, thanks.

So far the chronology looks like this?

1855 - waltz
1910 - Belden (mansion)
1927 - Darby (moonshine and Bessie)
1930 - Twenty-One Years
WWII - Stalag Luft III bomber crew version
1950 - Connemara Cradle Song
1960 - Borstal version

I was wondering, Lighter at work, where you might have picked up the WWII bomber crew verses?

Thanks everyone - my kids are now demanding an explanation for the song Polly-Wolly-Doodle (Mom, if Sal is a nickname for Susanna, who the heck is Polly? And who's the fairy fey he's saying goodbye too?)