Glyph and Origin

The glyph is a small loop opening into a long curving stroke, read traditionally as the lion's mane and sweeping tail, though some have taken the same curve for a lion crouched in profile; as with the other signs this pictorial reading is traditional rather than documented in an ancient source. Leo belongs to the twelvefold zodiac of Babylonian origin fixed in Hellenistic astrology, and Greek myth attached to the constellation the Nemean lion of the first labour of Heracles, whose hide no weapon could pierce.

The written form is first securely attested in the medieval Byzantine codices of Greek horoscopes, the manuscript tradition catalogued by Otto Neugebauer and Henry Van Hoesen, and it was regularised into a stable printed shape only once astronomical almanacs and ephemerides, following the lead of Regiomontanus's Kalendarium and Ephemerides out of his own Nuremberg press in the 1470s, began setting the zodiac signs consistently in type instead of by scribal hand. The tropical sign no longer overlaps the constellation of the same name, the two having drifted apart through the slow precession of the equinoxes, a wobble of the Earth's axis that shifts the equinoctial points roughly one degree every seventy-two years.