Eliot, check both "Deep The Water, Shallow The Shore" & "Black Jacks-Afro Americans Sailors". I don't believe this to be of only Irish or only Black making, but influenced by both. Both cultures had an extremely strong influence in the creation, spread & rise of the art of the work song at sea. During the Western Expansion the coastal water trades, of the full eastern seaboard & Islands, were dominated by Black Watermen, while the deep water trades by their white counterparts. Both worked the docks, rivers, etc. & traveled westward together or at the same point in time, to the point where the origins (of a good bit of the shanties) are from Brittish Isle/Irish/Afro/American/etc & can't, in some cases, be seperated, because the merger in the influences were so complete, complex & lost. As to words or wording used in shanties, a look into the language of the sea might be of some help. In short, whatever worked, for whatever reason, was used & kept as long as it's function continued. Function could be commands that didn't sound alike in the midst of a storm, short & sweet, clear as to their sound & meaning. We get phrases & words that last well past their usefull origins the bowline, from a once important line for sail handling to a now important knot, 'son of a gun', 'towing the line', 'cat-in the bag', 'freeze the brass balls off a monkey', port instead of the once used larboard. If Shenandoah or Missouri/Misery felt good to the singer or group/community it stayed if something else came by that fitted the scene, or I'd even say personnel preference, it may change. You could be on an endless dig, this could be an endless thread, good luck Barry