KJV uses “ghost” in two senses, for the human life force and for God’s Holy Spirit. KJV never uses “ghost” for the disembodied spirits of the dead. All 11 OT references involves the phrases “give up the ghost” (e.g., Gen 25:8; 35:29), which means to cease breathing or simply to die. This phrase occurs eight times in the NT (Matt 27:50; Acts 5:5; 12:23). The predominant NT use is for the Holy Spirit.
Modern translations uses “ghost” (rather than “spirit” as the KJV) for the disembodied spirits of the dead. Jesus’ disciples mistook Him for a ghost when He walked on water (Matt 14:26; Mark 6:49) and when He appeared after the resurrection (Luke 24:37,39).