Old English godspel "gospel, glad tidings announced by Jesus; one of the four gospels," from god "good" (see good) + spel "story, message" (see spell (n.)); translation of Latin bona adnuntiatio, itself a translation of Greek euangelion "reward for bringing good news."
The first element of the Old English word had a long "o," but it shifted under mistaken association with God. The word passed early from English to continental Germanic languages in forms that clearly indicate the first element had shifted to "God," e.g. Old Saxon godspell, Old High German gotspell, Old Norse goðspiall. Used of anything as true as the Gospel from mid-13c. Gospel-gossip was Addison's word ("Spectator," 1711) for "one who is always talking of sermons, texts, etc."
The first four books of the New Testament, which tell the life story of Jesus and explain the significance of his message. Gospel means “good news” — in this case, the news of the salvation made possible by the death and Resurrection of Jesus. The four Gospels are attributed to Matthew, Mark, Luke, and John.
Note: Figuratively, anything that is emphatically true is called the “gospel truth.”
The absolute truth: His book's the gospel