Sharyn - sychronicity is amazing. Just after posting I was leafing through Belden's collection of Ballads from Missouri and found a reference to a "goodnight" song from about 1905.

It was a song I'd never heard of - something like "McAfee's Lament" (not McPherson's). The reference to it was worded in such a way that I realized is was in common use way back then.

I envy you having studied folklore. It takes me 40 years to find out about these things with hit and miss reading and listening!