Why do some use the term Holy Ghost, which sounds like a ghost, rather than God the Holy Spirit?

Although the Holy Ghost is mentioned 90 times by that name in the King James Bible, many are turning from this name for the Holy Spirit. They see in "ghost" a picture of a spook or some form of Casper. The idea is that this connection is harmful to an understanding of the true nature of the Holy Ghost. Therefore, we must change the designation. Although many who question the use of the term are sincere believers, there are important reasons for retaining it. In several ways, Holy Ghost is the correct name for the third person of the trinity.

Verbally:

Holy Ghost is the correct name verbally. Historically, "ghost" is a synonym to "spirit." This was its only meaning in Old English. Not only do we see this meaning in the title, Holy Ghost, but also in the phrases, gave up the ghost (Genesis 25:8Then Abraham gave up the ghost, and died in a good old age, an old man, and full of years; and was gathered to his people.
See All..., 17; 35:29
See All...; Job 3:11Why died I not from the womb? why did I not give up the ghost when I came out of the belly?
See All...), and, yielded up the ghost (Genesis 49:33And when Jacob had made an end of commanding his sons, he gathered up his feet into the bed, and yielded up the ghost, and was gathered unto his people.
See All...; Matthew 27:50Jesus, when he had cried again with a loud voice, yielded up the ghost.
See All...; Acts 5:10Then fell she down straightway at his feet, and yielded up the ghost: and the young men came in, and found her dead, and, carrying her forth, buried her by her husband.
See All...). The ghost is the inner spirit or soul of a person. Although this meaning is not as commonly used today, it is the original and base meaning of the word.

Theologically:

Holy Ghost is the correct name theologically. Holy Ghost is one of the established theological names for the third person of the trinity. More and more, we are seeing doctrine attacked by the removal of established theological terms. The term, propitiation, which is rich in doctrinal meaning has been removed from many modern English versions. English books on theology and doctrine well into the twentieth century freely use Holy Ghost as the biblical term. When we remove this term from our vocabularies, we separate ourselves one step further from the teaching of those in the past who made the Bible their constant companion. The name, Holy Ghost, is used 90 times in the King James Bible. It is used in historical documents, doctrinal statements, and in libraries of books. When we allow God's people to become uncomfortable with these grand terms, we make them a bit dumber in understanding the richness of God's word.

Doctrinally:

Holy Ghost is the correct term doctrinally. Although the original meaning of ghost is spirit, the King James translators were not ignorant of the modern connotations. The word carried the meaning of a "disembodied spirit of a dead person appearing among the living" by the fourteenth century. It would have been well-known to the King James translators as having this meaning. Therefore, since they also used Holy Spirit (Luke 11:13If ye then, being evil, know how to give good gifts unto your children: how much more shall your heavenly Father give the Holy Spirit to them that ask him?
See All...) and could have easily used that term exclusively, there must have been a distinct reason for retaining Holy Ghost. Certainly, one of the reasons is that it was an established theological term. However, there may have been another reason.

We think of a ghost as the spirit of a dead person that appears among the living. This idea typifies the coming of the Holy Ghost. Jesus clearly taught that the Holy Ghost would come in a special way to the believers after His death and departure. John 16:7Nevertheless I tell you the truth; It is expedient for you that I go away: for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you.
See All... states, "Nevertheless I tell you the truth; It is expedient for you that I go away: for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you." The Comforter is the Holy Ghost (John 14:26But the Comforter, which is the Holy Ghost, whom the Father will send in my name, he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you.
See All...). He is the "Spirit of truth" (John 15:26But when the Comforter is come, whom I will send unto you from the Father, even the Spirit of truth, which proceedeth from the Father, he shall testify of me:
See All...) who will come to the saints after the body of Christ has departed. Also, just as the common ghost reminds us of the one who has departed, so the Holy Ghost will testify of Jesus Christ (John 15:26But when the Comforter is come, whom I will send unto you from the Father, even the Spirit of truth, which proceedeth from the Father, he shall testify of me:
See All...) and will glorify Him (John 16:14He shall glorify me: for he shall receive of mine, and shall shew it unto you.
See All...). So, although the Holy Ghost does not perfectly match the common idea of ghost today, there are some strong parallels that make the word especially insightful.

I can understand how the term Holy Ghost may seem strange to a new believer. However, the word has a grand history and an important meaning. It should not be removed. And, as with other things, the strangeness will disappear as you use it. Perhaps it will help that you now know some of the depth of its history and meaning.