Constantine m. Latin Constantinus, a diminutive of Constant, which by the early Middle Ages was treated as an independent name.
The name of a number Roman and Byzantine emperors, a legendary king of Britain, an 8th C pope, an 8th C antipope, a 9th C Byzantine saint, two 9th C kings of Scotland, a 10th C king of Scotland, six patriarchs of Constantinople, several early British saints, a 13th C prince of Novgorod, a 13th C tsar of Bulgaria, a 13th C king of Georgia, a 14th C Serbian ruler, four kings of Armenia, a 15th C king of Georgia.