Origin of the word
The Teutonic word Lent, which we employ to denote the forty days' fast preceding Easter, originally meant no more than the spring season. Still it has been used from the Anglo-Saxon period to translate the more significant Latin term quadragesima (French carême, Italian quaresima, Spanish cuaresma), meaning the "forty days", or more literally the "fortieth day". This in turn imitated the Greek name for Lent, tessarakoste (fortieth), a word formed on the analogy of Pentecost (pentekoste), which last was in use for the Jewish festival before New Testament times. This etymology, as we shall see, is of some little importance in explaining the early developments of the Easter fast.
Origin of the custom
Some of the Fathers as early as the fifth century supported the view that this forty days' fast was of Apostolic institution. For example, St. Leo (d. 461) exhorts his hearers to abstain that they may "fulfill with their fasts the Apostolic institution of the forty days" — ut apostolica institutio quadraginta dierum jejuniis impleatur (P.L., LIV, 633), and the historian Socrates (d. 433) and St. Jerome (d. 420) use similar language (P.G., LXVII, 633; P.L., XXII, 475).
But the best modern scholars are almost unanimous in rejecting this view, for in the existing remains of the first three centuries we find both considerable diversity of practice regarding the fast before Easter and also a gradual process of development in the matter of its duration. The passage of primary importance is one quoted by Eusebius (Hist. Eccl., V, xxiv) from a letter of St. Irenaeus to Pope Victor in connection with the Easter controversy. There Irenaeus says that there is not only a controversy about the time of keeping Easter but also regarding the preliminary fast. "For", he continues, "some think they ought to fast for one day, others for two days, and others even for several, while others reckon forty hours both of day and night to their fast". He also urges that this variety of usage is of ancient date, which implies that there could have been no Apostolic tradition on the subject. Rufinus, who translated Eusebius into Latin towards the close of the fourth century, seems so to have punctuated this passage as to make Irenaeus say that some people fasted for forty days. Formerly some difference of opinion existed as to the proper reading, but modern criticism (e.g., in the edition of Schwartz commissioned by the Berlin Academy) pronounces strongly in favor of the text translated above. We may then fairly conclude that Irenaeus about the year 190 knew nothing of any Easter fast of forty days.
The same inference must be drawn from the language of Tertullian only a few years later. When writing as a Montanist, he contrasts the very slender term of fasting observed by the Catholics (i.e., "the days on which the bridegroom was taken away", probably meaning the Friday and Saturday of Holy Week) with the longer but still restricted period of a fortnight which was kept by the Montanists. No doubt he was referring to fasting of a very strict kind (xerophagiæ — dry fasts), but there is no indication in his works, though he wrote an entire treatise "De Jejunio", and often touches upon the subject elsewhere, that he was acquainted with any period of forty days consecrated to more or less continuous fasting (see Tertullian, "De Jejun.", ii and xiv; cf. "de Orat.", xviii; etc.).
And there is the same silence observable in all the pre-Nicene Fathers, though many had occasion to mention such an Apostolic institution if it had existed. We may note for example that there is no mention of Lent in St. Dionysius of Alexandria (ed. Feltoe, 94 sqq.) or in the "Didascalia", which Funk attributes to about the yearkú yet both speak diffusely of the paschal fast.
Further, there seems much to suggest that the Church in the Apostolic Age designed to commemorate the Resurrection of Christ, not by an annual, but by a weekly celebration (see "the Month", April 1910, 337 sqq.). If this be so, the Sunday liturgy constituted the weekly memorial of the Resurrection, and the Friday fast that of the Death of Christ. Such a theory offers a natural explanation of the wide divergence which we find existing in the latter part of the second century regarding both the proper time for keeping Easter, and also the manner of the paschal fast. Christians were at one regarding the weekly observance of the Sunday and the Friday, which was primitive, but the annual Easter festival was something superimposed by a process of natural development, and it was largely influenced by the conditions locally existing in the different Churches of the East and West. Moreover, with the Easter festival there seems also to have established itself a preliminary fast, not as yet anywhere exceeding a week in duration, but very severe in character, which commemorated the Passion, or more generally, "the days on which the bridegroom was taken away".
Be this as it may, we find in the early years of the fourth century the first mention of the term tessarakoste. It occurs in the fifth canon of the Council of Nicea (A.D. 325), where there is only question of the proper time for celebrating a synod, and it is conceivable that it may refer not to a period but to a definite festival, e.g., the Feast of the Ascension, or the Purification, which Ætheria calls quadragesimæ de Epiphania. But we have to remember that the older word, pentekoste (Pentecost) from meaning the fiftieth day, had come to denote the whole of the period (which we should call Paschal Time) between Easter Sunday and Whit-Sunday (cf. Tertullian, "De Idololatria", xiv, — "pentecosten implere non poterunt"). In any case it is certain from the "Festal Letters" of St. Athanasius that in 331 the saint enjoined upon his flock a period of forty days of fasting preliminary to, but not inclusive of, the stricter fast of Holy Week, and secondly that in 339 the same Father, after having traveled to Rome and over the greater part of Europe, wrote in the strongest terms to urge this observance upon the people of Alexandria as one that was universally practiced, "to the end that while all the world is fasting, we who are in Egypt should not become a laughing-stock as the only people who do not fast but take our pleasure in those days". Although Funk formerly maintained that a Lent of forty days was not known in the West before the time of St. Ambrose, this is evidence which cannot be set aside.