Except Richard, we do.

Took me five mins on the ubiquitous Google to find that nonny and fol de rol etc have, historically speaking, a geographical aspect to them. (Seemed logical before I searched but hey ho (nonny nonny.).

Lots of speculation, including by Allan Taylor, that early collectors published and regional variations of the same root songs standardised to a degree, and some voice music (fol de rol etc) became more prevalent.

So yes, nonny nonny isn't known now compared to a couple of hundred years ago, but conversely, it appears those who sang nonny nonny would probably say "I have never heard a song with fol de rol in it!

Although Michael was around when both were prevalent so rather confused by his question 😎