So the St James Infirmary tune may have originated with Klezmer music?
That's amzing, it's the first time I've heard of that connection.

I wish I'd knew the name of the Yiddish tune, to take this research one step further.
It sure is fascinating how far both tune and words of St James Infirmary have travelled.
Despite quickly becoming a very commercial song it has all the makings of a folk song.

It reminds me a bit of Willie the Weeper in that regard.

Regarding the "cannonball" verse, it usually runs something like this:

I may die out on the deep blue ocean,
I may be shot by a big cannonball,
Now if you follow me to the end of my story,
You'll find a woman was the cause of it all.

Cannonball always seemed a bit out of place to me (even with the mention of the ocean), maybe it really is a corruption of bar room brawl.
I often wondered whether the expression "a woman was the cause of it all" was a hint that both he and his woman also died of veneral disease, like in the Unfortunate Lad.

Just some food for thought.