The Yoni

While the symbols of the male have claimed a worldwide
homage, the symbols of the female have by no means been
neglected, either by ancient Phallicism or by Christianity.
The usual and natural symbol of femininity is a doorway or
archway, suggestive of the vulva or external genitals. This is often
conventionalized into an oval, a circle, a crescent, a vesica piscis
or fish’s bladder (a term applied by architects to an oval church
window which narrows at top and bottom), a diamond-shaped
lozenge or an inverted triangle. Concerning this last symbol,
which is sometimes referred to as the Greek letter Delta, Inman
says:

The selection of name and symbol was judicious, for the
words Daleth (Hebrew) and Delta (Greek) signify the door
of a house, and the outlet of a river, while the figure
reversed, with the heavy side above, modestly represents
the fringe with which the human delta is overshadowed.

This sacred doorway of life, through which every human soul
must enter this world, has been deemed worthy by the Roman
Catholic Church to frame around the Blessed Virgin and Holy
Child, either as a vesica piscis or in some other conventionalized
form, unmistakably yonic.

(p. 241)