What is the 'NEW' evidence for shanty origins of shanty. Shanties have been used long before the 1800's. See The Tempest act one, by Will Shakespear which could be the earliest written English reference.
Perhaps an earlier reference in 1066 of sailors leaving Normandy using songs to work the ships.
Haul, haulage is the term to move loads. On land cotton pickers, stevadores, loggers. At sea on rivers or lakes. One thing they have in common is that they mainly travelled to the New world or Australia by ship for about 3 months or more. Hearing the same songs over that period then others when you land in dockland. Then you have the sailors who leave the harsh conditions of sea life to go ashore for a possible easier life.
I noted an earlier comment that Irish word for hut sounds like shanty just as in Breton (also a celtic language) chanter is a building site, or construction site. You must also keep in mind that French was not the first language of all the French. Each region had its own dialect in full use in the 1800's. I know several Bretons in their 70s and older where as children, breton was their mother tongue.
It is with good cause that many Irish gaelic words made it into American English as up until 1750 the majority of slaves in America came from Ireland. Even these would have been exposed to sailors worksongs.