Apparently there is a (false) legend that Valentine’s Day derives from the ancient Roman festival of the Lupercalia. I admit that I had never heard this one — but the excellent Bill Thayer has gone to some trouble to research it, so clearly it does.
He has also added an article from Classical Philology about the festival in the 5th century here. This contains a number of interesting statements, all derived from a letter of Pope Gelasius defending the abolition of the festival.
When it was finally abolished by the efforts of Gelasius, he addressed to a group of senators an epistle defending the step, which approximates the length of an apologetic treatise. He admits that the old pagan rite had continued under his predecessors, through the days of Alaric, Anthemius, and Ricimer, and had been abolished only in his own time; but he defends the earlier popes by saying that ills could not be healed at once, and that perhaps they had tried to remove this superstition but had failed to win the support of the imperial court. …
The Lupercalia, then, must belong to the class of superstitions which lingered on among a nominally Christian people. Something of the nature of this superstition may be learned from the letter of Pope Gelasius cited above.
1. As to the purpose of the Lupercalia. — A pestilence had broken out in Campania, which Andromachus and other senators ascribed to the suppression of the Lupercalia. The Pope replied that the purpose of the festival was not to avert pestilence but to promote the fertility of women; that pestilence and ills of every sort had been abundant while the Lupercalia continued; and that there was no connection between a city festival and happenings in Campania.
This reply raises a question as to the purpose of the rites. Gelasius cites an account from the second decade of Livy (292‑218 B.C.), to the effect that the Lupercalia was instituted to relieve the sterility of Roman matrons….
Now that sounds like an interesting letter! And uses the (lost) second decade of Livy as well? Hmmm….!
The notes say that it was published in the Collectio Avelana, in CSEL 35.1, p.390 f. But 390 is wrong — it is in fact letter 100, on p.453-464, to Andromachus.
The letter ought to be translated into English. My calculation is that it’s about 1,800 words long. I might see if I can find a translator on Student Gems.