What the sources claim for it
Attraction. The authority under which something is drawn rather than compelled.
History
Where does Venus come from?
The sign is conventionally described as a hand mirror, though that reading is late and may be a rationalisation of a Greek letter form. The planet takes copper — mined and worked on Cyprus, from which the metal's name comes, and Cyprus is Aphrodite's island, so the association is geographic as much as symbolic.
Its operations in the Solomonic material are love, friendship, and the winning of goodwill, which is exactly the register in which its opposition to Mars operates: attraction against force. The biological use, again, comes from Linnaeus in the eighteenth century.
Afterwards
What did it turn into?
Astronomical notation, the alchemical sign for copper, and the standard biological sign for female.
Which texts describe it?
Oldest first, with what each one does with the mark. A mark described in a Bronze Age incantation and a mark first drawn in a seventeenth-century manuscript are different kinds of claim, whatever the shape has in common.
The Key of Solomon (Clavicula Salomonis)
Anonymous; ed. S. L. MacGregor Mathers · 15th-16th c. · Latin and Italian
Pentacles of Venus for love and for favour, made in copper.
Read The Key of Solomon (Clavicula Salomonis) in full ↗Cover: Public domain · Unknown author · Wikimedia file page
Nearby
Related marks
Saturn
The scythe. Slowest planet, heaviest metal, and the authority a grimoire invokes for work involving binding, decay and the dead.
Jupiter
A stylised Greek zeta for Zeus. The sign of increase, favour and judgment in one's favour — the grimoires' preferred authority for asking.
Mars
Shield and spear, iron, Tuesday — and, since Linnaeus, the biological sign for male, which is a much later and quite separate job.
The Sun
A circle with a point at its centre — the oldest form in the set, and the one the alchemists used for gold without further explanation.
Mercury
A caduceus drawn as a glyph — the one sign in the set that names a metal, a planet and a god that all behave the same way.
The Moon
A crescent, silver, Monday — the planetary authority for anything involving dreams, water, change and things done at night.