The Roman Numeral II associated with Gemini stands for twins or “companion” and it also represents the “pillars of knowledge.” Since Gemini is ruled over by Mercury, they are known for having intelligence, ingenuity and artistic talent.
Mercury’s Symbol means “mind over matter.” The horns or moon crescent represents the winged helmet and intuitive strengths of Mercury/Hermes/Thoth over the circle of divine spirit and the cross of matter.
Gemini in mythology are the twins: Castor and Pollux. Castor and Pollux were born out of an egg because Zeus disguised as a swan, mated with Leda. The Twins were said to have been part of Jason and the Argonauts quest to find the golden fleece. The mortal brother Castor was killed in battle and the Demi god Pollux asked that his brother be saved. As a compromise both brothers were placed among the stars for eternity.