Ross-

I'm thinking that the term "bally" is commonly used in West Indies shanties, such as the rowing shanty "Hell of a Wedding on the Congo River":

Who do you think do the music for them?
Way, hey! Hey, me bully boys!
De bally band an' de drum fish playing,
Way, hey! Hey, me bully boys!

I'm not sure what "bally" means in that context either but evidently it's a positive adjective.

And it may have no relation to a "bally boat."

Cheerily,
Charley Noble