I said to Heart, "How goes it?"
Heart replied :
"Right as a Ribstone Pippin!"
But it lied.
    by Hilaire Belloc (1870-1953) , "The false heart", from Verses, published 1910

- from which it seems that a Ribstone Pippin is proverbially an apple on whose quality one can rely.

I have always wondered whether juber-ju has any connection with 'jube-jube' a jelly-sweet much beloved of children when I was one: thus imparting a sense of 'sweetness & soft amiablility' [as in addressing someone as 'sugar-lump'. I have known this song for many years from Peter Bellamy's 'Fair England's Shore' LP 1968, where he attributes it to Sam Larner.