Phantasm: something imagined; an illusion, or apparition; something that seems to exist, but, in fact, does not.
The Latin word for ghost is phantasma. It comes from the Greek φάντασμα (a phantasm), which derives from φαντάζω (I make visible).
The English word ghost comes from the German word is Geist , which means… ghost.
Lately, we’ve heard accordion music in our house at night. We fear we may have a polkageist in our home.