"...It's another word for friend." Well, maybe he's simplifying. But it isn't much more than that. Ghosts, being the formless parasitic undead creatures that they are, need an emotional tie to the world to maintain a sense of connection or presence, and what better way to do that than being that one friend who drains all your emotional energy? Well, maybe he's being cynical. But he's seen what happens when ghosts get clingy. It gets weird. "Did you imagine there was some sort of arcane ritual?"