Glyph and Origin

The glyph is a pair of upright strokes joined top and bottom, resembling the Roman numeral two and read as the paired figures standing side by side. The Greek myth names the twins Castor and Pollux, the Dioscuri, one mortal and one immortal, who chose to share their time between Olympus and the underworld rather than be separated; a comparable doubled figure appears still earlier in Babylonian star lists as the Great Twins, MASH.TAB.BA in the cuneiform sources, long before the Greek names were attached to the same stars. Like the other signs it descends from the Babylonian zodiac codified in Hellenistic astrology and no longer aligns with its namesake constellation, the gap widened over two millennia of precession.

The written form is preserved in the medieval Byzantine copies of Greek horoscopes studied by Otto Neugebauer and Henry Van Hoesen, and it reached the shape used today only after fifteenth and sixteenth century printers, following the example of Regiomontanus's early printed Kalendarium and Ephemerides out of Nuremberg, settled on a standard typeset rendering for the sign rather than leaving it to the freer hand of a manuscript copyist working letter by letter across successive copies.