Wikipedia
The Caprotinia, or feasts of Juno Caprotina, were ancient Roman festivals which were celebrated on July 7, in favour of the female slaves. During this solemnity they ran about, beating themselves with their fists and with rods. None but women assisted in the sacrifices offered at this feast.
Kennet says the origin of this feast, or the famous Nonae Caprotinae or Poplifugium, is doubly related by Plutarch, according to the two common opinions. First, because Romulus disappeared on that day, when an assembly being held in the Palus Caprae ("Goats'-Marsh"), suddenly a storm broke, accompanied with terrible thunder, and other unusual disorders in the air (see Plutarch's Life of Numa). The common people fled all away to secure themselves; but, after the tempest was over, could never find Romulus, their king.
Or, else, from Caprificus, a wild fig-tree, because, in the Gallic war, a Roman virgin, who was prisoner in the enemy's camp, got up into a wild fig-tree, and holding out a lighted torch toward the city, gave the Romans a signal to fall on; which they did with such good success, as to obtain a considerable victory.