February 15th is the date of one of the most ancient and long-lasting Roman religious festivals, the Lupercalia. It was originally instituted as a purification rite of the city, and called “Februa”, whence the name of the month in which it is held. The feast had its own priests, the Luperci, who would offer a sacrifice at an alter in the Lupercal, the cave at the base of the Palatine Hill in which the she-wolf (lupa) was said to have suckled Romulus and Remus. This was followed by a feast, after the priest would make thongs (known as februa) from the animals’ skin, and then run around the base of the hill holding them in their hands, and with them striking, those whom they encountered along the way. Plutarch reports the custom that women would deliberate stand where they might be so struck, since this was believed to help those who wished to conceive a child. This custom is mentioned in act 1, scene 2 of Shakespeare’s Julius Caesar, in which Caesar say to Antony, who is to run as one of the Luperci. “Forget not in your speed, Antonius, / To touch Calphurnia, for our elders say / The barren, touchèd in this holy chase, / Shake off their sterile curse.”
(The Lupercalia, ca. 1635, by the Italian painter Andrea Camassei, 1602-49; public domain image from Wikimedia Commons.)

After Caesar’s assassination, in the famous “Friends, Romans, countrymen” speech (act 3, scene 2), the Lupercalia is mentioned again, when Antony says, “You all did see that on the Lupercal / I thrice presented him a kingly crown, / Which he did thrice refuse. Was this ambition?” This is based on the following passage of Suetonius’ Divus Julius (79). (In Shakespeare, this episode is discussed at length by the soon-to-be assassins Brutus, Cassius and Casca, also in act 1, scene 2.)
“Adiecit ad tam insignem despecti senatus contumeliam multo arrogantius factum. Nam cum in sacrificio Latinarum, revertente eo inter immodicas ac novas populi acclamationes, quidam e turba statuae eius coronam lauream candida fascia praeligata imposuisset, et tribuni plebis Epidius Marullus Caesetiusque Flavus coronae fasciam detrahi hominemque duci in vincula iussissent, dolens seu parum prospere motam regni mentionem sive, ut ferebat, ereptam sibi gloriam recusandi, tribunos graviter increpitos potestate privavit. Neque ex eo infamiam affectati etiam regii nominis discutere valuit, quanquam et plebi regem se salutanti Caesarem se, non regem esse responderit; et Lupercalibus pro rostris a consule Antonio admotum saepius capiti suo diadema reppulerit atque in Capitolium Iovi Optimo Maximo miserit.
To an insult which so plainly showed his contempt for the Senate, he added a deed of even greater arrogance; for at the Latin Festival, as he was returning to the city, amid the extravagant and unprecedented acclamations of the people, someone in the crowd had placed on his statue a laurel crown with a white fillet tied to it; and the tribunes of the plebs, Epidius Marullus and Caesetius Flavius had ordered that the ribbon be removed from the wreath and the man be put in chains, Caesar, either offended that the hint at regal power had been received with so little favor, or, as he claimed, that he had been robbed of the glory of refusing it sharply rebuked and then deposed them. But from that time on he could not rid himself of the infamy of having aspired to the title of king, although when the plebs hailed him as king, he replied that he was Caesar, and no king; and at the Lupercalia, when the consul Antony several times attempted to place a crown upon his head as he spoke from the rostra, he pushed it away, and sent it to the Capitol (to be offered) to Jupiter Optimus Maximus.”