According to Megillat Taanit, in the 4th century BCE, Alexander the Great met Shimon HaTzaddik, the High Priest of the Holy Temple. Shimon feared that Alexander would destroy Jerusalem, so went out to meet him before he arrived at the city. Upon seeing the High Priest, Alexander made the rare move of dismounting and bowing. When asked to explain his actions, Alexander said that he'd previously seen the High Priest in a dream. Alexander interpreted this vision as a good omen and thus spared Jerusalem, peacefully absorbing Israel into his growing empire. In gratitude, the Sages decreed that the Jewish firstborn of that time be named Alexander -- which remains a Jewish name to this very day.