User blog comment:Lesdin/Darssan, the Inciter/@comment-24385282-20160225222332/@comment-3391671-20160226055212

If Jason wishes to know what it actually means (outside its name in the Fate series), it means "Demon" or "Angel from Hell" in the Arabic (?) culture. As True Assassin and the other Assassins (Hassan's) originate from that culture, the name makes sense in language and nature.