When I first saw the word, niddy nooddy, I remember thinking what the hell is that?
When I googled the word, this is what came up:
A niddy-noddy (plural niddy-noddies) is a tool used to make skeins from yarn. It consists of a central bar, with crossbars at each end, offset from each other by 90°.
And this is what it looks like
When you have finished spinning your yarn, you will need to remove your yarn from the bobbin, onto the niddy noddy to skein it.
For example, here is one of my finished yarns still on the bobbin
Here is an example of the yarn off the bobbin and wound around the backs of two chairs put side by side