Why is the Holy Spirit called Holy Ghost?

Answer 1

Probably the main reason is from the use of "Holy Ghost" in the King James Version of The Bible, though the term predates that translation. In English of the KJV era (early 1600s), "ghost" was not as limited in its meaning as it is in modern English, but meant generally the soul or spirit of a person or thing. It could also mean a "spirit" in the modern sense of a non-physical entity. The parallel German word "Geist," retains that broader meaning; it can mean a "ghost" in the modern English sense, but consider its use in the expression "Zeitgeist" = "spirit of the times".

We still have a few expressions that show this used to be true in English as well: to "give up the ghost" means to die, but it only makes sense if the "ghost" is something that the living possess in them. Also the phrase "ghost in the machine" (with all respects to R.E.M., it originated with Gilbert Ryle in 1949) is a philosophical term for the soul as distinct from the physical human body.

John Wycliffe's translation of the New Testament (1382) used "Holy Ghost" almost exclusively, and the major English translations between Wycliffe and the KJV (Tyndale, Coverdale, Bishop's Bible, Geneva Bible) do the same. The expression "Holy Ghost" was used in the Church of England's Book of Common Prayer (1559), but "Holy Spirit" was more frequent. In the Book of Common Order (1556) used by the expatriate English and Scottish Calvinists in Geneva, "Holy Spirit" is more common in the prayers and orders of worship, but in the confession of faith "Holy Ghost" is employed almost exclusively. It may or may not be significant that "spirit" is derived from the Latin "spiritus," while "ghost" is from Anglo-Saxon roots.

The KJV translators thus had two terms that were employed fairly interchangeably for a generation or two before them, but with an established tradition of "Ghost" in the English translations of the Bible. The KJV uses "Holy Ghost" 89 times, all in the New Testament, and "Holy Spirit" 7 times, 3 in the Old Testament and 4 in the New Testament. In each case the terms translate various forms of the same Greek phraseology, and for the 4 uses of "Holy Spirit" in the New Testament one can find multiple other instances where "Holy Ghost" was used for the same, or virtually the same, Greek phrase.

Another reason the expression "Holy Ghost" has remained is its use in worship texts where changing to "Holy Spirit" would be jarring, such as the well-known Doxology, "Praise Him above, ye heavenly host / Praise Father, Son and Holy Ghost."