The word for Christmas in late Old English is Cristes Maesse, the Mass of Christ, first found in 1038, and Cristes-messe, in 1131; in Latin Dies Natalis.
Early Celebration
Christmas was not among the earliest festivals of the Church. Sts. Irenaeus and Tertullian omit it from their lists of feasts, and Origen, glancing perhaps at the discreditable imperial Natalitia, asserts that in the Scriptures sinners alone, not saints, celebrate their birthday. Arnobius can still ridicule the "birthdays" of the gods.
The first evidence of the feast is from Egypt. About A.D. 200, Clement of Alexandria says that certain Egyptian theologians "over curiously" assign, not the year alone, but the day of Christ's birth, placing it on 25 Pachon (May 20) in the twenty-eighth year of Augustus. The December feast therefore reached Egypt between 427 and 433.
In Rome the earliest evidence is in the Philocalian Calendar, compiled in 354, which contains three important entries. In the civil calendar December 25 is marked "Natalis Invicti." In the "Depositio Martyrum" a list of Roman or early and universally venerated martyrs, under December 25 is found "VIII kal. ian. natus Christus in Betleem Iudæ."
De Santi (L'Orig. delle Fest. Nat., in Civiltæ Cattolica, 1907), following Erbes, argues that Rome took over the Eastern Epiphany, now with a definite Nativity colouring, and, with as increasing number of Eastern Churches, placed it on December 25. Later, both the East and West divided their feast, leaving Ephiphany on January 6, and Nativity on December 25, respectively, and placing Christmas on December 25 and Epiphany on January 6. The earlier hypothesis still seems preferable.
Origin of Date
Concerning the date of Christ's birth the Gospels give no help; upon their data contradictory arguments are based. The census would have been impossible in winter: a whole population could not then be put in motion. Again, in winter it must have been; then only field labour was suspended, but Rome was not thus considerate. Authorities moreover differ as to whether shepherds could or would keep flocks exposed during the nights of the rainy season.
Natalis Invicti
The well-known solar feast, however, of Natalis Invicti, celebrated on December 25, has a strong claim on the responsibility for our December date. For the history of the solar cult, its position in the Roman Empire, and syncretism with Mithraism, see Cumont's epoch-making "Textes et Monuments" etc., I, ii, 4, 6, p. 355. Mommsen (Corpus Inscriptionum Latinarum, 12, p. 338) has collected the evidence for the feast, which reached its climax of popularity under Aurelian in 274. Filippo del Torre in 1700 first saw its importance. It is marked, as has been said, without addition in Philocalus' Calendar. It would be impossible here even to outline the history of solar symbolism and language as applied to God, the Messiah, and Christ in Jewish or Chrisian canonical, patristic, or devotional works. Hymns and Christmas offices abound in instances; the texts are well arranged by Cumont.
Liturgy and Custom
The fixing of this date fixed those too of Circumcision and Presentation, of Expectation and, perhaps, Annunciation B.V.M., and of Nativity and Conception of the Baptist (cf. Thurston in Amer. Eccl. Rev., December, 1898). Till the tenth century Christmas counted, in papal reckoning, as the beginning of the ecclesiastical year, as it still does in Bulls. Boniface VIII (1294-1303) restored temporarily this usage, to which Germany held longest.
The Crib (creche) or Nativity Scene
Saint Francis of Assisi in 1223 originated the crib of today by laicizing a hitherto ecclesiastical custom, henceforward extra-liturgical and popular. The presence of ox and ass is due to a misinterpretation of Isaias 1:3, and Habakkuk 3:2 ("Itala" version), though they appear in the unique fourth-century "Nativity" discovered in the Saint Sebastian catacombs in 1877. The ass on which Balaam rode in the Reims mystery won for the feast the title Festum Asinorum (Ducange, op. cit., s.v. Festum).
Hymns and Carols