Empty Library Folder suddenly appears within the Document Folder

Yesterday, I started my MacBook (with the latest version of BigSur) to find an empty, locked (red "do not enter" symbol) "Library" folder in my Document folder. I have not installed or changed anything, that I know of. Nor can I access the folder, as

The folder “Library” can’t be opened because you don’t have permission to see its contents.

Can I retrace how it got there in some logs?

As it likely should not be there (and it's empty) – how can I remove it?