Four Calling Birds
I had a fascinating honors History of Western Civilization class in college that focused on "Rhetoric" and even though I took the course as a very underqualified freshman, its impact on me has been lasting. The professor, Dr. Gideon Burton, commented once that languages eventually climax and then deteriorate until they become new languages. My personal opinion is that the English language was at is best in the period between 1770 to 1850 and has since commenced its decline.
This "Four Calling Birds" situation is a perfect example and evidence of how easily we mess up our own language. The song was originally "Four Colly Birds". Colly, colley, collie, coaly all mean black, like coal. This stanza of the songs was about blackbirds, not beautiful singing birds! But I guess "Calling" birds sounds better when words like "colly" become archaic and the general public doesn't know what it means.
Apparently blackbirds baked into a pie in medieval times were a delicacy. But which blackbirds? Ravens, crows, starlings? Or does it refer to the bird known in England as the Blackbird that is not even related to the blackbirds most of us know, but more closely related to the American Robin, but not all related to what people in England know of as a Robin. Confused yet! Yeah, so is our language. Bah humbug!