In traditional Catholic circles, one often hears the term "Holy Ghost" rather than "Holy Spirit." Older Catholics remember the days when "Holy Ghost" was the way we called Him. That almost disappeared in the 1970s and after, and younger Catholics may find the term "Holy Ghost" a little strange.
I found it strange when I first heard it in the late 1960s. The only ghost I knew back then was Casper the Ghost. When I first heard the term "Holy Ghost," I thought of a good ghost, like Casper. But then somehow, even as a kid, I knew the Holy Ghost was God, and not a cartoon figure.
Later I learned that "ghost" is a very old English word, whose meaning went back a long, long time ago when it meant "spirit," a living being with no physical body. The angels are ghosts, according to the original meaning of the word "ghost." Our souls are ghosts, since they do not need to be attached to a body in order to live. As a matter, it's our bodies that need a soul in order to live. God is a ghost. If you think of "ghost" as a spirit-being, then you see there is no problem.
Only much later did "ghost" come to mean, among people, the spirit of a dead person, usually scary.
Our English word "ghost" comes from the same roots as the German word for "spirit," which is "geist." The Holy Ghost in German is "der Heilige Geist."
So, in older English Bibles, such as the Catholic Douay-Rheims Bible, when Jesus died and His soul left His body, the Bible says that Jesus "yielded up the ghost." (Matthew 27:50)
In some older books, I have read about lay people meeting on retreat for "ghostly purposes," meaning "for spiritual reasons." Prayer does good for our "ghostly lives," is another example.
SO WHY CONTINUE TO SAY "HOLY GHOST?"
1. If we should stop saying "Holy Ghost" because "ghost" presents a lack of precision or clarity, meaning more than one thing, then we have the same reality with the word "spirit," which can also mean more than one thing.
As a matter of fact, the normal meaning we give to "spirit" in ordinary conversation is "emotion."
How are his spirits today?
Sing with spirit!
Or perhaps an attitude. Where's our team spirit?
But the Third Person of the Trinity is not an emotion; He is a person. A person who is a pure spirit; a ghost, if you will.
In many a casual conversation I have had, even with Catholics, one gets the distinct impression that they think the Holy Spirit is the spirit of God the Father, not a person separate from the person of the Father. The word "spirit" is vague enough to make that impression on someone not well-grounded in the Trinity.
2. Why should we conform our church language to the vocabulary of the world at the moment, which is one way today and a different way tomorrow?
3. Because the world uses "ghost" in a different way nowadays, saying "Holy Ghost" identifies us more as religious people, different from the world. When people hear us say "Holy Ghost," it makes them curious because, to them, it is a strange phrase. Curiosity about our faith is good; it moves people to ask questions, learn and - perhaps - desire to have the same faith we have!
4. Using the term "Holy Ghost" connects us to centuries of Catholic tradition. Pick up any book in English about the Third Person of the Trinity written in the 1600s, 1700s, 1800s and up to the 1950s and chances are it will talk about the Holy Ghost.
5. In a sense, "ghost" denotes something about the Holy Spirit that we should never forget. Even in the ordinary sense of the word "ghost," there is the idea that ghosts come and go; appear and disappear. Jesus said the same thing of the Holy Spirit; He blows where He wills. If we are in the State of Grace, the Holy Ghost is always with us, as are the Father and the Son. All three Divine Persons are with us every moment in our sanctified souls. But even then the Holy Spirit can move in a new and different way; inspiring us, moving us, consoling us, strengthening us - but each time in a somewhat different way, just as our spiritual needs differ moment to moment. His movements come and go, and no one can predict when and how. This underscores the personality of the Holy Ghost; that He is a person, with free will. He is not some vague life "force" or impersonal "spirit", and since He is a person, He is a spirit whom we cannot harness and control.
WHAT ABOUT "HOLY SPIRIT?"
It's a perfectly acceptable term, as is "Holy Ghost." That's if we understand "spirit" to mean a person, and not "emotion" or "inner condition." We can, and do, use both terms in Catholic tradition. Just as "ghost" has to be understood in a religious sense, so does "spirit." Attaching the adjective "holy" to both "ghost" and "spirit" helps us do this. He is not just a ghost or a spirit; He is a specific person, the Third Person of the Trinity. He is THE Holy Spirit or Holy Ghost; the Divine Person we call the Holy Spirit or Holy Ghost.
ONE FINAL POINT
Even since the Second Vatican Council, it is not true that "ghost" was just not a suitable name anymore and we threw it out completely.
Why? Because time and time again we modern Catholics still sing a hymn that goes, "Come Holy Ghost, Creator blest, and in our hearts take up thy rest."
No one has a problem with it! Because we know what we mean when we say "Holy Ghost."
The world may not; but the world is welcome to join us.