While maybe not the best example, wanting to be brief and having no exact idea where to go I went to 1:1, start at the beginning....
Title and Introduction to the Book
The Revelation of John. The Greek word apokalypsis is usually rendered in English as “apocalypse” or “revelation” (NOTE on 1:1). Placing the name “John” in the title identifies him as the book’s author. Justin Martyr referred to “John, in a revelation that was given to him” (Dial. 81), using the term “revelation” for the message that was disclosed rather than a title for the work. Later, “Revelation” seems to have been used as the book title in contexts where John was assumed to be its author (Irenaeus, Haer. 4.14.2; 4.17.6; 4.20.11; 5.28.2; 5.35.2; Tertullian, Marc. 3.14.3; 4.5.2). Melito of Sardis (d. ca. 190) wrote a lost work on the devil and the Revelation of John (Eusebius, Hist. eccl. 4.26.2). The Latin translation of Irenaeus’s works (early third century) refers to the “Revelation of John” (PG 7.687A), while the fourth-century Codex Sinaiticus (א) introduces this work with the title “Revelation of John” (Apokalypsis Iōannou) and concludes with a subscription that uses the plural, “Revelations [Apokalypseis] of John.” Later manuscripts sometimes used expanded titles, such as “The Revelation of John the Theologian and Evangelist” (046). On authorship, see INTRO II.A.
The original “title” of this book was its opening line: “A revelation from Jesus Christ” (Rev 1:1). The separate title “Revelation of John” was added later, when the book was copied and preserved alongside other writings. Titles were sometimes placed on tags attached to the outside of a scroll, so a person could identify a scroll without unrolling it. Separate titles were also inscribed inside the scroll, usually at the end of a work but sometimes at the beginning. When works were bound together in a codex, they could be given a title at the beginning, at the end, or at both places (Turner, Greek, 16–17; Aune 1:3–4; Kraft 17–18).
In the first century the term “apocalypse” was used for the disclosure of something hidden, but it was not a technical term for a literary genre. The prominence of the word “apocalypse” at the beginning of John’s work apparently contributed to the use of this term as a title for visionary writings. The Muratorian canon fragment (either late second or fourth century CE) referred to the “apocalypses of John and Peter,” indicating that the two were similar types of writings. “Apocalypse” was also used for visions of Peter (Clement of Alexandria, Ecl. 41.2; 48.1; 49.1; cf. Eusebius, Hist. eccl. 6.14.1) and in the titles affixed to works known as the Apocalypse of Paul, the Testament of Abraham, 3 Baruch, the Greek Apocalypse of Ezra, and the Apocalypse of Sedrach (Denis, Concordance, 830, 866, 871, 873). Since the manuscripts that bear these titles are rather late, it is uncertain whether the texts originally called themselves “apocalypses” (M. Smith, “History,” 19).
By the late second and third centuries a number of Christian texts claimed to present revelations. To distinguish these works from each other, they were given titles referring to the people who were said to have written them. To some extent, this is appropriate for Revelation, since 1:1–3 identifies John as the recipient of the visions and in 1:4 John addresses the readers in his own name. Nevertheless, the traditional title Apokalypsis Iōannou focuses on John as the writer, but the initial words Apokalypsis Iēsou Christou identify Jesus as the giver of the revelation and the authority for the message (Schüssler Fiorenza 39–40).
Craig R. Koester, Revelation: A New Translation with Introduction and Commentary, ed. John J. Collins, vol. 38A, Anchor Yale Bible (New Haven; London: Yale University Press, 2014), 209–210.