εὐαγγέλιον euangelion, a Greek word meaning good news.
History
The Priene Calendar Inscription says, "...Caesar, by his appearance excelled even our anticipations, surpassing all previous benefactors, and not even leaving to posterity any hope of surpassing what he has done, and since the birthday of the god Augustus was the beginning of the good tidings for the world that came by reason of him."
Before the time of Christ, Caesar Augustus was described as the bringer of the gospel.
(Hillsdale College - Ancient Christianity)
The Gospels were written by A.D. 60-100. For the 1st century, the Gospels had a local and independent existence in the constituencies for which they were composed before they began circulating throughout the church. By the beginning of the 2nd century, the Gospels were brought together and circulated as a fourfold record, detaching Acts from Luke and circulating on its own.
(The Origin of the Bible: Newly Updated by F. F. Bruce, J. I. Packer, Philip W. Comfort, and Carl F. H. Henry, 2020. Biblical Languages by Larry Walker. Section One: The Authority and Inspiration of the Bible by F. F. Bruce. Page 9; The Canon of the New Testament by Milton C. Fisher, Pages 76-77.)
Literary Form
Technically, the Gospels are an expanded hero story. They consistently keep the focus on Jesus, and their narrative purpose is to tell the story of the teaching and deeds of Jesus. The plot is not single but episodic, and the organizing principle is loosely chronological. The majority of the text is devoted to Jesus' three-year public ministry, and a fourth is devoted to the trial, crucifixion, and resurrection.
Jesus makes claims that conventional heroes do not make: possessing the power to forgive sins, that He will lay down His life for the salvation of His followers, that He will rise from the dead, and that He is the light of the world. His deeds of power transcend hero stories.
The combination of forms is without parallel. Equal space is given to what the hero said and did. Within the narrative framework are continuous examples of common genres like parable, drama or dialogue, sermon or oration, and saying or proverb. Narrative subtypes abound: annunciation and nativity, calling or vocation stories, recognition stories, witness stories, pronouncement stories, miracle stories, and passion stories.
(The Origin of the Bible: Newly Updated by F. F. Bruce, J. I. Packer, Philip W. Comfort, and Carl F. H. Henry, 2020. The Bible as Literature by Leland Ryken, Page 124-125)