It was May month, named for our ancestors (maiores),
And a relic of the old custom still continues.
When midnight comes, lending silence to sleep,
And all the dogs and hedgerow birds are quiet,
He who remembers ancient rites, and fears the gods,
Rises (no fetters binding his two feet)
And makes the sign with thumb and closed fingers,
Lest an insubstantial shade meets him in the silence.
Fasti, Book V
Some people say May was named for Maia, an earth goddess, but I think Ovid is a more trustworthy source. And if you’re one of those remembering the ancient rites (i.e. the head of your household), you must get up tonight, make that weird sign with your hand while you wash it in spring water; and then walk through your house throwing black beans behind you while saying, nine times, “With these beans I throw I redeem me and mine.”
Fortunately, the ghostly ancestors will collect the beans for you, but you’re not done yet – you still have to clang some bronze and say, nine times, “Ancestral spirit, depart!”
Then get some rest, because this is just the first day of the three-day festival, which ends on May 13 (it skips the even-numbered days, which were unlucky).