I must correct an embarrassing error I made earlier. I misattributed the 19th century examples of "chantey" and "shanty." Nordhoff DID spell "chantey-man" in 1856 - the earliest known example. The journalist writing in 1869 was the first we know of to spell it "shanty."

Many apologies for this blunder.

We don't know for certain how Nordhoff (an American) pronounced what he spelled as "chantey."   We do know there's only one way to pronounce 1869 "shanty."