From Barbara G. Walker, The Woman's Encyclopedia of Myths and Secrets, p. 1097:
"Vulva," the primary Tantric object of worship, symbolized variously by a triangle, fish, double-pointed oval, horseshoe, egg, fruits, etc.
Personifying the yoni, the Goddess Kali bore the title of Cunti or Kunda, root of the ubiquitous Indo-European word "cunt" and all its relatives: cunnus, cunte, cunning, cunctipotent, ken, kin, country.
The Yoni Yantra or triangle was known as the Primordial Image, representing the Great Mother as source of all life. As the genital focus of her divine energy, the Yantra was adored as a geometrical symbol, as the cross was adored by Christians.
The ceremony of baptismal rebirth often involved being drawn bodily through a giant yoni. Those who underwent this ceremony were styled "twice-born."