Track #4 on His ND Xmas is "O! Santa" by Chatham County Line, from Yep Roc's Oh Santa! holiday compilation.
I guess it could even be called the "title track" of the album, even though the song and album have different punctuation. I've checked the song title on the internet, and the correct title really is "O! Santa", as in capital-O, exclamation point space Santa. There are a few Christmas carols ("O Little Town of Bethlehem", "O Come All Ye Faithful" and "O Come O Come Emmanuel" come to mind) that start with a single "O", which I think is an alternate for "Oh!". So this song means something like "Oh! it's Santa".
The band Chatham County Line is a folk, bluegrass ensemble that doesn't use amplification or microphones (kind of like Asylum Street Spankers), but they aren't complete bluegrass purists since their latest album was produced by Chris Stamey, and one of their first hits on youtube is this bluegrassified cover of "I Got You (I Feel Good)". And the next is a Wilco cover.
They don't have any performances of "O! Santa" on youtube, but the Oh Santa is available on emusic and amazon and all the usual places, as are all four of their albums. They're from Raleigh NC but Chatham County is in Southeast GA -- I don't know what's up with that?