The origin of the design has many sources. The symbol to the left is the representation of the “Female” and is also the planetary symbol for Venus named after the Roman Goddess of Love. Many authors claim that it is derived from the hand mirror held by the Goddess Venus but this is increasingly disputed.
A further explanation is that it a stylized version of the Greek symbol “Phosphoros”. It is more likely that this is a far more ancient sexual symbol that has been sanitised in recent centuries. One belief is that the circle represents the womb and the cross below represents the vagina. Inverted, the cross symbolises the “Gloria” and the circle represents the vaginal canal. It certainly looks more like a stylisation of the female genitalia than a spurious hand mirror. Just remember that many of the facts you were taught in school were “revised’ by the puritan educationalists of the 18th to 20th centuries.