Hand print (20000 BCE, Cave of Pech-Merle, France).

Dactyls-"Fingers"-were born from the fingerprints of the Goddess Rhea: five males from the print of her right hand, five from the print of her left hand. Their Greek name was derived from Sanskrit Daksa, "dextrous one," a Hindu god of the hand.

Mano pantea, the Hand of the All-Goddess, was a sacred fetish of many examples have been found in the ruins of Pompeii and Herculaneum. It always showed the thumb and first two fingers raised, the last two fingers folded down. Middle finger, index finger, and thumb invoked pagan trinities of Father-Mother-Son, such as Jupiter-Juno-­Mars, or Osiris-Isis-Horus. The same kind of trinity, consisting of God, Mary, and Jesus, used to be worshipped by eastern Christians- which ­may explain why Christianity adopted the mano pantea and named it "the hand of blessing."

"Hand of God", fresco from San Clement of Tahull, Barcelona, Spain (Romanesque 9th - 12 century).

Bonaventura Berlinghieri, Episodes of the life of Saint Francisco, Capella Bardi, Florence, 
Italy (13th century).

The gesture was displayed by Christian priests and by emperors or kings by way of benediction and expression of their own union with the land, they captured. (Land  belonged in ancient matriarchy times  exclusively to the female.)

The thumb was the child, or child-soul symbolized in such fables Hop-0-My-Thumb. The index finger was the Mother, the one pointed, controlled, cast spells. The middle finger was the Father, a phallic symbol for thousands of years, up to and including the present day.

Arabs used to cut open a vein of the middle finger with a stone knife when making a pledge of faith, invoking a curse of castration if the pledge be broken. Roman male prostitutes used to signal potential customers by thrusting the middle finger into the hair of their heads. 

Fresco from the Tomb of the Lionesses in Tarquinia, Italy (Etruscan, about 500 BCE).

Oddly enough, but typically for patriarchy, the classic finger-sign of the devil didn't use the middle finger at all, but displayed his "horned head" by pinning down the middle and fourth fingers with the thumb and extending the index and little fingers. On the well-known magic principle that an evil sign was prophylactic against evil, this gesture was often used in Italy and the Balkans as a defense against the evil eye.

Like most European symbols, it seems to have originated with matriarchal Kali Ma, who owed it as a mudra (sacred gesture) in her manifestation as Jagadamba, "Mother of the World." Obviously it was meant to signify her own horned head embodied in the sacred cow.

Kali Ma with the symbol of the half moon / cow horns.

The most revered mudra was the one meaning "infinity" or "perfection," and most generally associated with female genitalia: thumb and forefinger pressed together at the tips, the other three fingers extended - our modern OK sign. 

Tantric yogis and bodhisattvas made this gesture in token of contemplative ecstasy. Persian sacred amulets of the Sassanian period (3rd century B.C.E.) showed a hand in this position, flanked by horns of fertility. The joined thumb and index finger formed a vesica piscis, immemorial symbol of the yoni, while the three extended fingers certainly referred to the Goddess's trinity.

Western Europe inherited the Egyptian idea that the index and middle fingers stood for the mother and father, respectively.

Egyptian mummies were buried with a protective amulet invoking both parents, called the Amulet of the Two Fingers.

The index or "mother" finger was the most magical. This was the finger that guided, showed, beckoned, called for attention, blessed, and cursed.

Medieval Christians feared the pointing of a witch's index finger, which is why children are still taught that it's rude to point, and why a woman's characteristic scolding gesture brandishes the index finger like a weapon. In Tantric tradition, this mother-finger was known as "the threatening finger." 

Andrea del Castagno, Sibyl of Cumae. Florence, Italy (15th century).

Matthias Grünewald, Crucifixion. 
Part of Isenheim Altar. 
Colmar, France (1515).

All Indo-European traditions knew it was female. (And patriarchal men used it to get the magical power. As everybody knows, it doesn't work. 
It only looks completely ridiculous.)

Arabs said the index finger represents the Goddess Fatima, whose symbolic Hand is still revered as a mystic summary of "the whole religion of Islam." 

Jewish patriarchs insisted on fettering a woman's threatening, spell-casting right index finger with the wedding ring, and orthodox Jewish women wear a wedding ring on that finger to this day. Christians, however, copied their wedding-ring custom from the pagans, who said a mystic "love vein" ran directly from the fourth finger of the left hand to the heart, therefore this finger should be bound in marriage. Macrobius wrote that a woman's wedding ring should be placed on that finger "to prevent the sentiments of the heart from escaping."

We have old symbols everywhere around us. Open your eyes and be aware, where those symbols are used. Very often they manipulate people and are turned in their opposite meaning or are perverted otherwise.
Don't let this intoxicate you.

Modern example:

Carlo Carr? (1881-1966), Hermaphroditic Idol. Milan, Italy.