Crist is the name of a trio of 10th century Old English poems concerning Jesus Christ, originally from the Anglo-Saxon "Exeter Book". The constituent poems are named Christ I, Christ II, and Christ III; the former two written by Cynewulf. They concern topics such as Christ's advent and ascension.
The character Eärendil, who at the end of the First Age was responsible for the intervention of the Valar and their subsequent defeat of Morgoth's, originated from an experience Tolkien had in 1913 when he read a particular line of Christ I:
Eala éarendel engla beorhtast
ofer middangeard monnum sended
In English, this nearly means Hail Éarendel, brightest of angels, sent over middle-earth to mankind!
Tolkien stated (through a character in The Notion Club Papers) that upon reading these lines he "...felt a curious thrill as if something had stirred in me.....There was something very remote and strange and beautiful behind those words, if I could grasp it, far beyond the ancient English." This inspiration is noted undisputably by scholars to have been important in the early formation of Tolkien's legendarium, if not its first cause, as Eärendil was the first committed character to take shape. This revelation from Christ I prompted Tolkien to write "The Voyage of Éarendel the Evening Star", a poem of which he would write five successive versions starting in September of 1914. From this poem would later stem The Tale of Eärendel, which too evolved in multiple schemes and emendations, but was never completed. It became the fifteenth of the posthumously published Lost Tales, and it was implied by its narrator, the character Gilfanon, to be the great culmination of all tales preceding it.
The Tale of Eärendel would also become the climax of Quenta Silmarillion: the chapter "Of the Voyage of Eärendil and the War of Wrath", in which Eärendil indeed journeys across Middle-earth to and from the West, seeking and gaining the aid of the Valar, and carrying the morning star across the sky. Millennia afterwards, Frodo Baggins and Sam Gamgee invoked Eärendil in different instances - calling him "brightest of stars" - in the Quenya outcries Aiya Eärendil Elenion Ancalima! and Aiya elenion ancalima! Eönwë's exclamation when greeting Eärendil in Aman, at the end of the First Age, also alludes to the couplet from Christ I.
The couplet also inspired Tolkien's use of the term "Middle-earth".
- John Garth, Tolkien and the Great War, Part One, Ch. 2, pg. 44
- Advent Lyrics (Christ I), Section 5 - https://anglosaxonpoetry.camden.rutgers.edu/christ-i/
- J.R.R. Tolkien: A Biography, pg. 72 (1978 paperback edition)
- Tom Shippey, The Road to Middle-earth, ch. 7: "Visions and Revisions", Eärendil: A Lyric Core
- Colin Duriez, J.R.R. Tolkien: The Making of a Legend, ch. 5: "The Shadow of War", pgs. 77-78
- Tolkien: A Celebration, 2: Stratford Caldecott, "Over the Chasm of Fire: Christian Heroism in The Silmarillion and The Lord of the Rings", pg. 22
- Peter Kreeft, The Philosophy of Tolkien, ch. 3: "Angelology", pgs. 71-72
- The History of Middle-earth, Vol. II: The Book of Lost Tales, chapter V: "The Tale of Eärendel", I, pg. 267
- J.R.R. Tolkien: A Biography, pg. 71 (1978 paperback edition)
- The History of Middle-earth, Vol. II: The Book of Lost Tales, chapter IV: "The Nauglafring", pg. 242
- The Lord of the Rings, The Two Towers, Book Four, Chapter IX: "Shelob's Lair"
- the Lord of the Rings, The Return of the King, Book Six, Chapter I: "The Tower of Cirith Ungol"