Stan Hugill, in Shanties From The Seven Seas, cites shanties from the 1840's that were a combination Black and Irish origin. Both groups, situated in the gulf states of the U.S. borrowed from each other. Hugill has some background information to go with each song. Originally published in the UK by Kegan Paul ltd., it can be found in paperback in the U.S., re-published by the Mystic Seaport Museum. Well worth reading. Good luck on your very interesting project. Please keep us informed on how it's going, eh?