Bob and leeneia,

Thanks for your thoughtful responses.

So true, Bob, about history and oral transmission.

Leeneia, indeed, I may be worrying too much! Still, our American minstrel humor was often at the expense of black people, which I would not want to propagate. However, their humor appears to have been broad, to say the least, and if this last verse is a sick joke, it's pretty subtle and likely would have been lost on much of the audience. A "playful ending to an innocent song" fits with the fact that the term "true blue" also occurs in the second verse, "I'd catch her a bird with a wing of true blue". Mr. S.S. Steele sure liked that alliteration!

In any event some good folks (eg. John Hartford; Tom, Brad & Alice) have sung this without it sticking in their craw; maybe it oughtn't stick in mine.