Galiana (I) is the feminine form of the Latin name Galianus.
Gherardesca (I) is the feminine form of Gherardo, an archaic form of Gerard (brave spear).
Giletta (I) is a feminine form of the English name Giles, which derives from Latin name Aegidius and Greek word aigidion (young goat), via Old French Gidie and Gilles. A very gutsy woman in The Decameron has this name.
Ginevera, Ginevria (I) is a form of Guinevere (white phantom).
Girolama (I) is a feminine form of Jerome (sacred name).
Galasso (I) is a form of Galahad, which is of unknown etymology.
Galeotto (I) is a form of Galehaut, an Arthurian name also of unknown etymology. Though it’s very similar to Galahad, the names are unrelated.
Galileo (I) comes from the Medieval Latin word Galilaeus, which in turn derives from Greek Galilaios (from Galilee). The ultimate root is the Hebrew word galal (roll), referring to the rolling of the Sea of Galilee (called Lake Kineret in Hebrew).
Gesualdo (I) may derive from Ancient Germanic name Giswald. The first element may derive from Gallo–Celtic root gaiso (spear) or be a short form of gisel (pledge, hostage), and the second element comes from Gothic root valdan (to reign). This name may also be a combination of Gesù (Jesus) and Ancient Germanic root wald (rule).
Grifone (I) means “griffin,” a legendary creature with the wings and head of an eagle and the tail, body, and back legs of a lion.
Gualfredo (T), Galfrido (I) is a form of Ancient Germanic names Walahfrid, derived from roots walha (stranger) and frid (peace), and Waldfrid, from Gothic root valdan (to reign) and Old High German fridu (peace).
Guilelmo (T) is a form of Guglielmo, the Italian form of William (will helmet).