Hi, Cori. I played the tune you posted on Facebook, and I know I've heard it before. However, I found 'The Lament for Owen Roe O'Neill' at the site called The Session, and their version is nothing like it.

Here's what I think happened: I think Ethel Crowninshield wrote a poem called 'Smiling Little Lass', and somebody came along, read the poem, and said, "Hey, you could sing this to the old tune 'Such-and-such!'"

I'll make a MIDI of your tune so people can hear it, and perhaps a Mudcatter can identify it.