Just as with the shanties themselves, the word was probably never written down until it became common usage among the (mostly) illiterate sailors.
Just take a look at how the spelling of the titles, and even the titles themselves, change so much from one collector to another.
The tunes used can vary considerably too!
So why rant at how Shantie Shanty Chanty or Chantie is spelled?
And that's just in English! (I wonder if there was a German chantey singer doing the same thing in Bremerhaven???)
There aint no right nor no wrong way about it.
Different ships, different long splices (as some old fella called Hugill was apt to say about it all).



Oh yeah, and its spelled Shannendoh, OK?    :-)