Your system doesn't drag folders into the dock, and the folders don't appear in the dock, unless you dragged them there. Are you saying that you don't have any idea what folders you put there?
Does any folder name appear when you mouse across those folders (even if the folder won't open, it may show the name of the folder.
If you have an exernal drive, then drag a folder from that drive into the dock -- then eject that drive, the folder remains, but can't open when the external drive is not mounted. Any possibilities there?