I do believe in ghosts! Maybe not the corporeal kind or the ones that chase you when you turn away from them. But the notion of "ghosts" arises from the connection between memory and death.
Suppose we spent a week together and I told you that, though your body will live on, you won't remember me or anything that happened during the time we spent together, including what I am telling you now? Psychologically it is death. Since "forgetting" is dying, then "remembering" must be what "lives on". Colloquially we speak of "remembering ourselves" when undergoing a trial in pursuit of an aim, for instance. But who is the rememberer? Is it one person or many? And can the memory itself take on a "life" which is more real than the actual life being remembered? That is a ghost.
So a "ghost" in one sense is "the living past", but it is also "dead meaning". It is used this way by Stirner, for instance, but as an idea it appears in myths and folk tales long before he appropriated it. And not always in a negative sense, either! There's a fable by R.L. Stevenson where a man is lead by a spirit to dig up the cairn of his ancestors, from which he receives instructions he doesn't understand but which will lead him to his destiny (meeting the mother of his unborn son, who is the 'leading spirit').