There are many kinds of ghosts, so I will consider some. Attention, since the ghost here is based on its own definition at this web site, please read "Ghost" first if you are unread.
I think that our ancestors were not stupid. They will not name things that do not exist. The ghost exists.
It was virtualization to create logical things from physical ones. Is the reverse possible? I will list my ideas.
The term virtual reality became common. Virtualization as an information processing technology is also evolving. However, we were also master of virtualization.
UFO stands for Unidentified Flying Object. In the past, the UFO was definitely existed. In modern times it may be like a difficult heritage of disposal.