https://www.newadvent.org/cathen/09152a.htm
> For example, the historian Socrates (Church History V.22) tells of the practice of the fifth century: "Some abstain from every sort of creature that has life, while others of all the living creatures eat of fish only. Others eat birds as well as fish, because, according to the Mosaic account of the Creation, they too sprang from the water; others abstain from fruit covered by a hard shell and from eggs. Some eat dry bread only, others not even that; others again when they have fasted to the ninth hour (three o'clock) partake of various kinds of food". Amid this diversity some inclined to the extreme limits of rigor. Epiphanius, Palladius, and the author of the "Life of St. Melania the Younger" seem to contemplate a state of things in which ordinary Christians were expected to pass twenty-four hours or more without food of any kind, especially during Holy Week, while the more austere actually subsisted during part or the whole of Lent upon one or two meals a week (see Rampolla, "Vita di. S. Melania Giuniore", appendix xxv, p. 478). But the ordinary rule on fasting days was to take but one meal a day and that only in the evening, while meat and, in the early centuries, wine were entirely forbidden. During Holy Week, or at least on Good Friday it was common to enjoin the xerophagiæ, i.e., a diet of dry food, bread, salt, and vegetables.
> There does not seem at the beginning to have been any prohibition of lacticinia, as the passage just quoted from Socrates would show. Moreover, at a somewhat later date, Bede tells us of Bishop Cedda, that during Lent he took only one meal a day consisting of "a little bread, a hen's egg, and a little milk mixed with water" (Church History III.23), while Theodulphus of Orleans in the eighth century regarded abstinence from eggs, cheese, and fish as a mark of exceptional virtue. None the less St. Gregory writing to St. Augustine of England laid down the rule, "We abstain from flesh meat, and from all things that come from flesh, as milk, cheese, and eggs." This decision was afterwards enshrined in the "Corpus Juris", and must be regarded as the common law of the Church. Still exceptions were admitted, and dispensations to eat "lacticinia" were often granted upon condition of making a contribution to some pious work. These dispensations were known in Germany as Butterbriefe, and several churches are said to have been partly built by the proceeds of such exceptions. One of the steeples of Rouen cathedral was for this reason formerly known as the Butter Tower. This general prohibition of eggs and milk during Lent is perpetuated in the popular custom of blessing or making gifts of eggs at Easter, and in the English usage of eating pancakes on Shrove Tuesday.
