In the dentist's today a (very) young mum had had brought her (I guess) 12 or 18 month old daughter, The little one (not olde enough to talk properly) was happy as larry in the play area pushing a plasic bus round and singing at the top of her voice "big shi ally alley o as ay ast ay ao ep ember"

Mum looked young enough to be my grandaughter and I was fascinated to see our culture so demonstrably being passed through the gerenerations. I learned the song as a child from my mother (a native of Liverpool, and graduate of the university of life) more than sixty years ago.

Looking for the origins of the song I ended up here.

From what I can see it has connections with shipping, and ties in to Liverpool especially, possibly tyneside too. Some associate it with the Manchester ship canal that linkes the cotton industry in Manchester with the sea, and that could be so, regarding the canal as a new form of "alley"

I was interested by the suggestion from martin above that the alleo might be shorthand for the Atlantic Ocean, and for my own contribution, I could easily see it as a shanty used to mark time by sailors working the ropes on rigged ships. Given the connection with Liverpool and the Atlantic, and the references to sinking and drowning, I suspect it pre-dates the ship canal.