For in-page table of contents, the table of contents is automatically generated based on the contents of H tags used on the wiki page. If the entry is displaying incorrectly, I need to know the source content of the first H tag so I can debug it.
For book table of contents, the table of contents is automatically generated based on pages that were added to the book. If there is a mysterious "Wiki" entry in the book, it is probably an old entry (it probably had a different title) that you deleted by another means, and its ghost is there awaiting the delete process to fully propagate to the remaining nodes (like this book). If this doesn't seem to take place, you might be able to remove the mysterious entry by using the "Manage Chapters" tab for the book and using the Delete option there.