The previous post brought another song to mind. Lavender Blue has pretty normal if fanciful lyrics but with nonsense words thrown in as often happens in traditional ballads.
The song Bonny Birdie is to some extent the same, but with some odd Scottish brogue thrown in. The word "diddle" appears frequently. But then there are verses like this:
"Then wi good white bread an farrow-cow milk
He bade her feet me aft
An ga her a little wee simmer-dale wanny
To ding me sindle and saft
"But wi good white bread an farrow-cow milk
I wot she fed me nought
An wi a little wee simmer-dale wanny
She dang me sare and aft."
That means: he told his lady to feed the bird with white bread and milk from a cow who hasn't given birth and he gave her a little stick of green wood to hit the bird seldom and soft. But the woman didn't feed the bird and hit it with a stick hard and often. It's no wonder the bird turned on her.
This is a great song, and is in Volume I of the Child Ballads (where I learned what the goofy lyrics mean).