Replacing Deleted Objects
If you ever create a wiki channel and then decide that it should be a page, you might have found yourself trying to find a new name for it, since the old name had a "~1" tacked on the end. There is a reason for this, and it can be escaped!
The URL gets the numeric addition, even if the old object was deleted because the old object secretly still exists! A deleted object lives in the Trash Can for 30 days after it is deleted, and it can be restored to its former glory (and URL) at any time. What that means is that the URL is reserved until it gets cleaned out of the Trash can.
You can circumvent this by restoring the object from the trash can, renaming it, and then deleting it again. (Or if you're super organized about it, you can also rename the object before you delete it.) This frees up the name for a new object to be created to your heart's content.