Spinney is a nice word for a smallish gathering of trees, alongside copse, coppice, etc. I’m not aware of a term for one specifically in an open field, though.

Apart from the hole, that could be chicken on a raft, an old Royal Navy dish.

I don’t think I’ve come across that before, but I’d say it depends on what is meant:

• I don’t know what that thing is.
• There is a thing, but I don’t know what it is.
• There is a thing such that I don’t know what it is. I.e., I do not know what all things are.

There may well be some other ones, but I don’t know what they might be.

Oddities and Curiosities of Words and Literature by C C Bombaugh, one of my favourite reads, feels like it might be an obscure book.

Thank you for this brilliant transcription. It’s as good as the image itself.

But wouldn’t ‘leery’ make sense there? It means something close to ‘suspicious’ after all.