Am thoroughly enjoying this thread!!
The backslang you talk about we used to call "pig latin" and used it a lot as kids. I can still do it a bit, but have to think about it!!
I remember some of those rhymes too, and they came from my 5th generation Australian mother who was of mainly Irish descent. Goodness knows where she got them from.
There was one she couldn't remember except for the last line and I wonder if anyone could fill me in on it (after puzzling about it for most of my life)?
It ended up with "and when he hop he fly". Mum could never go back any further than that, but the silly line ended up as a pretty common family saying - meaning absolutely anything, but usually nothing at all

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Philippa