Mano Fico

The Mano Fico (fig hand, properly, ‘mano fica’) is an ancient obscene gesture, and is also one of the better known protective gestures against the eye. The thumb and fist gesture is an ancient representation of sexual union. The name is from the Italian word for the female vulva, fica,meaning fig (and also the origin of a well-known English obscenity).
The fig was associated by the Romans with female fertility and eroticism; the fruit was sacred to Bacchus. The gesture is used against the evil eye in the belief that an obscenity serves as a distraction to evil, even that demons are so repelled by the notion of sex and reproduction that they flee at the sign,

Symbol Dictionary