Thanks for the link, stallion.

There are two issues here.

The first is, "Where does 'juberju' (etc.) come from?"

The second is, "What does it mean?"

"Jump up on her juberju" sounds like it an echo of "jump(ing) Juba." A "a proper juberju" could be the next stage of misunderstanding. Maybe a "proper juberju" is an alteration of a "proper jubilee," changed arbitrarily for the rhyme. Beyond that, who knows? The derivation is essentially unknown.

A search of various databases finds no appearances of "juberju" (etc.) outside of versions of this song. That means that if it ever "meant" anything in particular, that "meaning" may have been known only to the creator of the original lyrics. The anarchic tone of the Bodleian broadside suggests that it's just a joke and means nothing at all.

With so little evidence, it's impossible to say much more. The fact that enormous book and newspaper databases don't turn up any "juberjus" outside of the song means that the average 19th Century singer/audience didn't know any more about it than we do.

In a hundred years, someone may well ask, "What's the real meaning of A-wop-bop-a-loo-bop-a-lop-bam-boom?" It's just a string of sounds.