From the Latin name Sebastianus, which meant "from Sebaste". Sebaste was the name a town in Asia Minor, its name deriving from Greek σεβαστος (sebastos) "venerable" (a translation of Latin Augustus, the title of the Roman emperors). According to Christian tradition, Saint Sebastian was a 3rd-century Roman soldier martyred during the persecutions of the emperor Diocletian. After he was discovered to be a Christian, he was tied to a stake and shot with arrows. This however did not kill him. Saint Irene of Rome healed him and he returned to personally admonish Diocletian, whereupon the emperor had him beaten to death.
Due to the saint's popularity, the name came into general use in medieval Europe, especially in Spain and France. It was also borne by a 16th-century king of Portugal who died in a crusade against Morocco.