Holy Ghost

Until c. 1500 Middle English forms were typically a combined holigost, haligast, etc., despite deriving from Old English forms which were always two words (hālga gāst, hālig gāst, etc.), calque of Latin Spiritus Sanctus, which in turn is a calque of Ancient Greek Πνεῦμα τὸ Ἅγιον (Pneûma tò Hágion), from πνεῦμα (pneûma, “breath, vital force, soul”) + ἅγιος (hágios, “holy”)).

Holy Ghost

1. (Christianity) The aspect (hypostasis) of the Trinity or Godhead corresponding to divine essence, which becomes present in and among the faithful (particularly inspired prophets) and is considered to proceed either (Eastern Orthodoxy) from God the Father alone or (Roman Catholicism) from Him together with God the Son
   • 1728, A Manual of Prayers and Other Chriſtian Devotions, “The Litany of the Saints and Angels”, page 50:

     O God the Holy Ghoſt, Perfecter of the Elect, Have Mercy on us.

• God the Holy Ghost
• See others at Holy Spirit

Holy Ghost (uncountable)

1. The plant Angelica archangelica.